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The present invention relates to slitting tools for longitudinally slitting cables. Particularly, the present invention relates to slitting tools for slitting the longitudinal web connecting the strand with the duct of an aerial interduct cable.
Cables having a strand and a duct are increasingly utilized in aerial applications where a multitude of wires and/or optical fibers need to be encapsulated and suspended between telephone poles. A cross section of a representative prior art aerial interduct cable 10 is shown in FIG. 1. The cable 10 conventionally features two cable profile portions 11, 12. The first cable profile portion 11 well known as the strand may encompass a suspension core 14, which may be a steel cable or the like. The second cable profile portion 12 well known as the duct may encompass a tunnel 15 for encapsulating conductive wires and/or optical fibers. The two profile portions 11, 12 are commonly combined via a web having web grooves 13.
Installation of aerial interduct cables often takes place under harsh conditions and under considerable time pressure. Prior to affixing the cable 10, a technician has to slit the cable 10 along its web such that the cable 10 may be hung with the suspension core 14 onto mounting hooks that are affixed at the telephone poles. Penetrating the web and slitting the tough web material takes considerable effort with a conventional knife or other primitive tools commonly used by technicians, bearing a high risk of bodily injury of the technician. Another unfavorable side effect of using conventional slitting tools is a high risk of inadvertent penetration of the tunnel 15 which may need to be avoided to maintain the tight tunnel 15 leak-proof in case of a consecutive pressure air assisted insertion of optical fibers. Therefore, there exists a need for a specialized cable slitting tool that minimizes manual force for penetrating and slitting the web and provides for a precise alignment of the slit in the middle of the web. At the same time, the tool needs to be compact in size and easy and save to operate. The present invention addresses these needs.
A cable slitting tool for longitudinally slitting a cable web features at least one but preferably two guide rollers having a roller circumference fitting a groove of the cable's longitudinal web such that the rollers are guided along the groove while the rollers are pressed against the groove by a cutting feature in the preferred configuration of a circular blade, which penetrates the web from a side opposite the guide rollers. The guide rollers are rotationally free held in a top body and the circular blade is held in a base body. Base and top body are slide ably adjusted and tightened with respect to each other by a tightening screw. The bodies are held in alignment to each other by preferably two guiding columns of one body slide ably guided in corresponding holes of one other body. The circular blade's cutting plane is substantially aligned with respect to the rollers' rolling direction such that it is aligned with its cutting edge with the web groove once the rollers snugly press on the web groove.
The cable slitting tool is brought in operational position by fitting its rollers onto one of the two web grooves while the two bodies are in distant position. An additional sliding guide of the bodies provides for correct angular orientation of the cable slitting tool during tightening of the screw until the blade begins to penetrate the opposite web groove. Once both bodies touch, the blade is at its operational penetration depth and the sliding guide is closed around the corresponding cable profile section.
While the tightened cable slitting tool is pulled along the web, the circular blade slits the web. The cutting edge is shaped to wedge in slitting direction the web between itself and the guide rollers resulting in a continuous pressure of the web onto the guide rollers. In that way, alignment is maintained during the slitting.
The cutting feature is preferably a circular blade either rotating and/or may be fixed in various angular positions. In case of the rotating circular blade, cutting friction is additionally reduced. The fixed blade may be applied in combination with softer and/or highly elastic cable materials whereas the rotating blade may be employed in case of hard and/or more brittle cable materials.
The sliding guide provides for additional safety against inadvertent run out of the guide rollers, which may otherwise occur in case of excessive natural bend of the web. The cable slitting tool may be attached via an attachment line to the operator, which may prevent tool loss at exposed locations.
FIG. 1 is a representative cross section of a prior art aerial interduct cable.
FIG. 2 is a first perspective view of a cable slitting tool having a continuously fitting sliding guide.
FIG. 3 is a front view of the prior art cable of FIG. 1 together with the cable slitting tool of FIG. 2 in open condition positioned on the cable prior to blade penetration.
FIG. 4 is similar to FIG. 3 except that the cable slitting tool is depicted in tightened configuration with the blade fully penetrating the cable web.
FIG. 5 is a second perspective view of FIG. 4.
FIG. 6 is a third perspective view of FIG. 4 with the cable web being partially slit.
FIG. 7 is a view in direction along the slit onto the cable of FIG. 1 with the cable slitting tool having flat guiding faces.
As in FIGS. 2-7, a cable slitting tool 100 for slitting a cable 10 has at least one but preferably two guide rollers 160 rotating around their respective axes 162. Each of the guide rollers 160 has a roller circumference 161 fitting a groove 13 of a longitudinal web of the cable 10 such that the rollers 160 are guided along the respective groove 13 while the rollers 160 are pressed against that groove 13. The cable slitting tool 100 further includes a cutting feature 150 in the preferred configuration of a circular blade. The cutting feature 150 has a cutting edge 151 facing the roller circumferences 162.
The cutting edge 161 is preferably curved and planar. For the purpose of this invention, a cutting plane CP is defined as a plane coinciding with the cutting edge 161 and being substantially symmetric with respect to a well known blade angle at with a blade of the cutting feature 150 tapers towards the cutting edge 161. The cutting plane CP is substantially parallel with roll direction RD of the guide rollers 160. The roll direction RD is the direction along which the slitting is performed. As a result, the cutting feature 150 assists in keeping the cable slitting tool 100 aligned with the web grooves 13 during the slitting operation where the tightened cable slitting tool 100 is moved along the web. The cutting edge 151 may also be in a wedge angle WA with respect to the roll direction RD. The cutting edge 151 is preferably configured such that the majority of its portion that operationally penetrates the web is in a wedge angle WA between more than 0 and less than 90 degrees. Irrespective its preferred configuration, the cutting edge 151 and/or the cutting feature 150 may have any other configuration well known in the art for cutting plastic and/or rubber and/or other materials commonly employed for cable housings.
The cable slitting tool 100 further includes elements and features for adjusting a distance between the cutting edge 151 and the roller circumferences 161. Such elements and features include a base body 110, a top body 120, alignment features 112, alignment fits 122 and a tightening feature 130. Both bodies 110, 120 are adjustable in distance with respect to each other. The guide rollers 160 are rotationally free held in the top body 120. The cutting feature 150 is held in the base body 110. The preferably two guide rollers 160 are substantially aligned with respect to each other such that they roll along their respective groove 13 in roll direction RD. The cutting feature 150 is positioned on the base body 110 such that it penetrates the web between the two guide rollers 160.
In case of a single guide roller 160, the cutting feature 150 is positioned such that it penetrates slightly behind the single guide roller 160 with respect to the roll direction RD. A resulting tilting torque may be opposed by a sliding guide 111, 121 described in detail further below.
The base body 110 is aligned with respect to the top body 120 in adjustment direction via at least one but preferably two alignment features 112 slide ably fitting in corresponding alignment feature fits 122. The alignment features 112 are preferably guide columns and the alignment feature fits 122 are preferably holes. It may be well appreciated by anyone skilled in the art that alignment features 112 and alignment feature fits 122 may have other well known configurations providing either sliding alignment or pivoting alignment. Pivoting alignment may be accomplished for example by a hinged connection between alignment feature 112 and alignment feature fit 122 in an offset to both guide rollers 160 and cutting feature 150 such that an angular movement between the bodies 110, 120 may result in a distance change between guide rollers 160 and cutting feature 150. In the FIGS. 2-7, the alignment feature 112 is part of the base body 110 and the alignment feature fit 122 is provided by the top body 120. The scope of the invention includes embodiments in which the alignment feature 112 may be part of the top body 120 and the alignment feature fit 122 provided by the base body 110.
The tightening feature 130 is preferably a screw having a knob 131, a screw flange 132, a screw thread 133 and an optional unscrew stopper 134. The tightening feature 130 is preferably manually actuated via the knob 131 for a simple and quick distance adjustment. During tightening of the tightening feature 130, the screw thread 133 screws in a corresponding thread hole of the base body 110 and presses with its screw flange 132 on the top face 125 of the top body 120 such that the cutting edge 151 is forcefully approaching the roller circumferences 161 and penetrating the web. The penetration force is opposed by the guide rollers 160 forcing them into pressed and aligned contact with one of the two grooves 13.
The cable slitting tool 100 may also include a sliding guide 111, 121 at least loosely corresponding to at least one of the cable profile portions 11, 12 but preferably to the first cable profile portion 11, which is commonly significantly smaller in diameter than the second cable profile portion 12. This provides for a minimized overall size of the cable slitting tool 100, which in turn makes the cable slitting tool 100 more easy to handle. Loosely corresponding and loosely trapped in context with the present invention means that there remains a gap between the bodies 110, 120 and the first cable profile portion 11 irrespective an eventual natural bend of the cable 10 as it may result from storing the cable 10 rolled up on a cable drum as is well known in the art.
The sliding guide 111, 121 is preferably provided by both bodies 110, 120 such that preferably the first cable profile portion 11 is loosely trapped between the base body 110 and top body 120 while both bodies 110, 120 are tightened such that contact faces 114, 124 are touching. This can be seen in FIGS. 4 and 7. Alternately, the first cable profile portion 11 may be easily released from the sliding guides 111, 121 in opened position of the bodies 110 as shown in FIG. 3. The tightened sliding guides 111, 121 may loosely trap the first cable profile portion 11 along two axes as depicted in FIGS. 4-6. This means, that the first cable profile portion 11 is limited in its movement within the tightened sliding guides 111, 121 in directions X1, X2, Y1, Y2. This is accomplished by the sliding guides 111, 121 overlapping the first cable profile portion 11 substantially more than 180 deg. Full two axes entrapment may be favorable in cases of a web groove only slightly smaller in height than the outer diameter of the first cable profile portion 11.
Alternately and as shown in FIG. 7, the tightened sliding guide 111, 121 may loosely trap the first cable profile portion 11 along one and a half axes. This means, that the first cable profile portion 11 is limited in its movement within the tightened sliding guide 111, 121 in directions X1, Y1, Y2. This is accomplished by the sliding guide 111, 121 overlapping the first cable profile portion 11 up to 180 deg. The scope of the invention includes embodiments in which the sliding guide 111 and/or 121 limits less than one and a half axes down to only a half axis X1. Half axis entrapment may be favorable in cases of deep web grooves 13 as may be well appreciated by anyone skilled in the art.
In case of only a half axis limitation the cutting feature is solely secured against inadvertent penetration of the tunnel 15. Two axes limitation and one and a half axes limitations allow for a tight integration of the sliding guides 111, 121 into and compact dimensioning of both bodies 110, 120. One or both of the sliding guides 111, 121 may feature flat contact faces as depicted in FIG. 7. The flat contact faces may be a horizontal faces 111H, 121H or vertical faces 111V, 121V. Flat contact faces 111H, 121H, 111V, 121V are easier to fabricate and provide in the corner regions more buffer space for debris.
The cutting feature 150 in its preferred configuration as a circular blade may be rotatable held around its symmetry axis 152. The symmetry axis 152 is preferably parallel to the roller axes 162 and perpendicular to the adjustment direction AD. Instead of being rotatable, the circular blade may also be fixed on the base body 110 in an adjustable fashion around the symmetry axis 152 such that portions of the circular blade are alternately brought into cutting orientation. In that way, the cutting blade may be worn off in steps. A rotatable circular blade may be employed in case of hard and brittle web materials such that the rotating blade motion may assist in decreasing the required slitting force. The fixed circular blade may be employed in case of soft and/or highly elastic web materials that require chafing cutting motion to prevent residue material being pulled over the cutting edge instead of being fully cut.
Configuration and assembly of guide rollers 160 and cutting feature 150 may be accomplished in manifold well known fashions by use of axles, shafts, retaining rings and the like. Structural elements are thereby preferably kept on the side of the bodies 110, 120 that is opposite the rollers 160 and blade 150 such that sufficient clearance is warranted towards the second cable profile portion 12. The base body 110 may feature a blade cover 113 covering the peripheral portion of the circular blade 150.
The cable slitting tool 100 may also include an attachment line 140 configured for attachment of the cable slitting tool 100 at an operator's body in general and an operator's waist belt in particular. The attachment line 140 may be fixed via an attachment feature 170 of the cable slitting tool 100 such as a hook or a bridge. The attachment line 140 may be of sufficient length for uninhibited operation of the cable slitting tool 100 within the operator's reach. The attachment line 140 may feature a well known snap hook (not shown) or the like on its peripheral end for a simple and quick securing and disconnecting at/from the operator's waist belt. The attachment line 140 may be particularly feasible in combination with any aerial hand tool. An aerial hand tool in context with the present invention is any hand tool operated at an exposed location or any hand tool where an increased risk of tool loss due to its dropping exists during its operational use.
Referring to the FIG. 3, the cable slitting tool 100 is initially brought into contact with its guide rollers 160 on one of two opposing web grooves 13, while both bodies 110, 120 are in a released distance. The optional unscrew stopper 134 may limit excessive separation of the two bodies 110, 120. Once the roller circumferences 161 touch one of the two grooves 13, the circular blade 150 may be aligned with the opposite groove 13. The alignment of the cutting feature 150 is established by contacting the top sliding guide portion 121 with the first cable profile portion 11. While the cutting feature 150 is kept in alignment, the cable slitting tool 100 is tightened by rotating the knob 130 and screwing in the screw thread 133 into the base body 110 until the contact faces 114, 124 touch. Once the cutting edge 151 begins to penetrate the web, the cutting feature 150 keeps itself in alignment. The cutting feature 150 is shaped and positioned on the base body 110 and with respect to the guide rollers 160 such that the cutting edge 151 slightly rises above the fully penetrated web as can be seen in FIG. 5 while the bodies 110, 120 are tightened. In that way, a complete slitting of the web is warranted. The cutting feature 150 is preferably also positioned so that in tightened position, the cutting edge remains preferably clear of the roller circumferences 161 to avoid damage of the cutting edge 151 and/or the roller circumferences 161.
The tightened cable slitting tool 100 may be preferably manually forced along the longitudinal web whereby the cutting feature 150 fully slits the web, which is shown in FIG. 6. During the slitting, guide rollers 160 and cutting feature 150 are primarily in contact with the cable 10. The wedge angle WA results in a wedging of the web between the guide rollers 160 and the cutting edge 151 during the slitting of the web in slitting direction RD. Thereby, the guide rollers 160 are continuously pressed against and kept in alignment with their respective groove 13. Only in case of cable bend and/or grossly misaligned application of slitting force, the sliding guide 111, 121 may additionally assist in keeping the cutting edge 151 in the center of the web. Once the slitting is completed, the tightening screw 130 may be loosened again and the circular blade 150 pushed out of the slit by pressing on the top of the knob 130. An optional spring (not shown) between the bodies 110, 120 may additionally assist in separating the bodies 110, 120. The secured guiding of the tightened cable slitting tool 100 in longitudinal direction of the cable 10 together with the blade cover 113 provides for a save operation with a minimum risk of bodily injury.
A cable slitting tool 100 was made from steel materials for slitting a well known aerial interduct cable 10 commercially available under the name “Duraline Figure 8”. The cable slitting tool 100 had an overall length 100L of about 3 inches and an overall height 100H in tightened condition of about 2 inches. The roller circumferences 161 had an approximate diameter of about 1 inch and an approximate width of 0.093 inch. The cutting feature 150 was configured as rotatable circular blade having a cutting edge 151 diameter of about 1.33 inches. A lubricant of the type Westek Bio Lube was applied to the aerial interduct cable 10 prior to slitting.
Accordingly, the scope of the invention described in the specification above is set forth by the following claims and their legal equivalent: