Patent Application
20130264085
This invention relates to hydraulic tools of the kind used by electric utility workers to cut, crimp, or spear cables. It relates more particularly to a hydraulic tool, comprising a power unit and a working head, in which the working head can be interchanged with other working heads, so that the power unit can be used with any of various heads, or so that a given working head can be used with any of several different power units.
In the installation and maintenance of electric power cables it is common practice to connect lengths of conductor by inserting ends of the conductors into a tubular metal connector, which is then crimped onto the conductors to connect them together permanently. Because spans of cable are typically quite heavy, the connectors must be strong enough to sustain the high tensile forces, and are therefore necessarily resistant to deformation. It follows that large crimping forces, typically 6 tons or more, are required. The most practical way to produce such large forces is to use hydraulic pressure.
The necessary hydraulic pressure can be generated by a battery powered pump housed along with a battery in the tool itself, by a hand operated pump, or by hydraulic fluid supplied under pressure from a pump separate from the tool.
Similarly large forces are required to operate cutting tools, of which there are various different kinds, some designed for cutting hard wire, and others designed for cutting soft wire.
Cable spearing tools are also operable by hydraulic pressure. In an electric power distribution system, when a particular cable is deenergized for replacement or for maintenance of the cable or electrical equipment fed by the cable, it is important for worker safety to ensure that the cable is not accidentally reenergized. To this end, the cable is grounded by inserting a metal device known as a “spear”, through the sheath of the cable and into contact with the conductor or conductors within the sheath. The spear either connects the internal conductor or conductors to the sheath itself or to another ground point. Spearing tools are similar to crimping and cutting tools.
An electrical utility worker or work crew typically requires several separate hydraulic tools, at least one for crimping, several for cutting, and at least one for spearing. If the workers want to be able to choose from among battery power, hand power and external hydraulic power, a still larger number of separate tools is required.
Although the cutting, crimping and spearing head portions of the tools are different from one another, the hydraulic pumps, pistons and related components can be identical. Nevertheless, tools utilizing a common power unit and interchangeable heads have not been made available. It has also been desirable to make the cutting, crimping, and spearing heads rotatable relative to the hand-held part that contains the pump, the operating piston and related components, so that the tools can be more easily used in manholes and other restricted environments. The desirability of rotation has presented an obstacle to the use of interchangeable heads.
This invention addresses the problem of interchanging heads on a hydraulic tool and at the same time making the heads rotatable. Another aspect of the invention affords further improvements on the versatility of the hydraulic tool.
A hydraulic tool in accordance with the invention comprised, as its principal components, a head and a power unit. The head includes a movable operating member. In most cases, the head will include an anvil, which can also be described as a fixed die, and a movable operating member in opposed, spaced relationship to the anvil, and a guide rigidly connected to the anvil. In those cases, the movable operating member is slidable in the guide toward and away from the anvil. The movable operating member can also be described as a movable die. The head also includes a receiver, which is also rigidly connected to the anvil, for removable connection of the head to a power unit. The movable member is accessible through a passage in the receiver.
The power unit comprises a hollow cylinder, a hydraulic fluid inlet port, and a piston slidable in the cylinder along the axis of the cylinder. The piston and the cylinder form a hydraulic fluid chamber in which, when hydraulic fluid is introduced into the chamber under pressure through the inlet port, it exerts a force urging the piston toward the anvil.
The cylinder is fitted to the receiver for connection of the head to the power unit, and the receiver and the cylinder are relatively rotatable about the axis of the cylinder through a range of angles when the cylinder is fitted to the receiver. The receiver and cylinder have interlocking lugs that prevent the head from being disconnected from the power unit when the receiver and the cylinder are relatively disposed at each of a plurality of angles in said range of angles but allow the head to be removed from the cylinder at least at one angle within the range. The receiver and cylinder include a releasable lock for maintaining the head and the power unit in a fixed relationship to each other at each angle of the plurality of angles at which the receiver and the cylinder are relatively disposed.
The power unit includes a second guide for preventing rotation of the piston about the axis of the cylinder while allowing reciprocating sliding movement of the piston relative to the cylinder. The piston extends through the passage in the receiver, and is connected to the movable member of the head. The movable member and the piston also have interlocking lugs preventing the movable member from being disconnected from the piston when the receiver and cylinder are relatively disposed at each of the above-mentioned plurality of angles and allowing the movable member to be disconnected from the piston when the receiver and cylinder are relatively disposed at least at one angle. The movable member can be a cutting blade, a crimping die, a cable spear, or any other die capable of being pressed by a piston in order to exert a force on an object. The movable member can also be any of various other devices, such as a toggle linked to a pair of opposed blades in such a way that movement of the toggle causes the blades to move toward or away from each other. In this case, the movable member exerts force on an object indirectly, the direct force being exerted by the blades.
In one embodiment of the invention, the piston is a hollow piston having a closed end adjacent and connected to the movable member of the head, and an open opposite end. In this embodiment, the second guide includes a hollow tubular member extending into the interior of the piston through the open opposite end of the piston. The hollow tubular member has a first end fixed to an end of the hollow cylinder, and having an open opposite end. At least one of the piston and hollow tubular member has a longitudinal slot extending from its open end at least to an intermediate location along its length, and a guide pin, fixed to the other of the piston and hollow tubular member extends radially into the longitudinal slot and fits the slot, thereby preventing rotation of the piston relative to the cylinder. In a preferred embodiment, the guide pin is fixed to the piston and the slot is formed in the second guide. Two such guide pins and two such slots can be provided, the two guide pins extending into different slots.
In accordance with another aspect of the invention, first and second relief valves are connected by fluid paths to the hydraulic fluid chamber and responsive to fluid pressure in the hydraulic fluid chamber, the first relief valve is set to open when said fluid pressure exceeds a first level and the second relief valve is set to open when said fluid pressure exceeds a second level higher than said first level. A valve is arranged to close off the fluid path that connects the first relief valve to the hydraulic fluid chamber. The valve is switchable from an open condition to a closed condition to control the maximum force exerted by the movable member.
The tool according to the invention affords a number of advantages, especially rapid and easy interchangeability of heads, rapid and easy interchangeability of power units, and other advantages depending on the particular embodiment or embodiments adopted. These other advantages may include ease of use, simplicity, reduced manufacturing cost, improved reliability, and versatility, as well as still other advantages.
Further details and advantages of the invention will be apparent from the following description when read in conjunction with the drawings.
The tool according to the invention comprises two basic components, a head and a power unit. The head and the power unit can be disconnected from each other so that the head can be interchanged with other heads for different purposes, all usable with the same power unit, and so that particular head can be used with any of several different power units, e.g., a battery-operated power unit, a power unit operated from a remote hydraulic fluid supply, or a hand-operated power unit.
A cylinder 24 fits into the receiver 20 and is held in the receiver by the cooperation of sets of lugs, which will be described. A piston 26, slidable in the cylinder 24 is provided with a protrusion 28, which has lugs for connection to the movable member 22. Although, in the preferred embodiment shown, the cylinder 24 fits into the receiver 20, various alternative configurations are possible, such as a configuration in which the cylinder has a tubular part with internal connecting lugs that cooperate with external lugs on the receiver portion of the head.
In
The lugs on the outside of the cylinder are preferably formed so that their outer surfaces are convex and in the form of portions of a cylinder having a diameter slightly less than the diameter of the inner wall of the receiver. Similarly, the lugs on the inside of the receiver are preferably formed so that their innermost surfaces are concave and in the form of portions of a cylinder having a diameter slightly greater than the diameter of the outer wall of the cylinder of the power unit on which the power unit lugs are formed.
Lugs 80 cooperate with lugs 86 on protrusion 28 of piston to connect the piston to the movable member. When the power unit is to be engaged with the head, the movable member 22 and the piston can both be in their fully withdrawn positions. To engage the head 12 with the power unit 14, the cylinder 24 of the power unit is inserted into the receiver 20 of the head while the head and power unit are in one of the six rotational relationships such that the lugs 88 on the cylinder can pass through the spaces between lugs 84 in the receiver. When the cylinder is inserted into the receiver, the lugs 86 on the protrusion of the piston also pass through the spaces between the lugs 80 in the recess of the movable member 22. Then, by rotating the head relative to the power unit by 30°, the lugs are brought into interlocking relationship. The interlocking relationship can be maintained by using a releasable lock, comprising a locking pin, to secure the head against rotation relative to the power unit.
The lugs on the protrusion of the piston and the lugs in the recess of the movable member can have cylindrical surfaces similar to those of the lugs on the power unit cylinder and in the receiver.
The locking pin 90 is shown in
As shown in
The guide 66 is secured to the end of the cylinder by fastener 104, which also secures retainer 102 in place. The guide has two slots 106 and 108, which extend axially from open end 110 of the guide to a location adjacent the opposite end 112 of the guide. Pins 114 and 116, which are fixed to the piston, extend radially inward into the respective slots 106 and 108, and prevent the piston from rotating in the cylinder while allowing the piston to move axially. Hydraulic fluid introduced through connector 46 flows through passage 118 in the cylinder and through an opening 120 in the end of guide 66 into the cylinder.
Referring again to
A manually operable selector toggle 154 can be rotated 180° to move a spindle 156 of valve 150 against a biasing compression spring 158 from a first position, shown in
If relief valve 146 is set to open at a pressure lower than the pressure at which relief valve 142 opens, the selector toggle 154 can be used to set the maximum force exerted by the movable member of the tool. For example, the tool can be set to exert a force of 12 tons when the valve 150 is closed, and a force of 6 tons when the valve is open.
The combination of the interchangeability of the heads and interchangeability of the power units with the force selection capability provides the user with an extremely versatile tool, making it unnecessary for the user to have on hand a large number of self-contained hydraulic tools, e.g., a battery-operated 6 ton crimper, a battery-operated 12 ton crimper, a battery operated soft wire cutter, etc.
There are many possible variations of the tool in accordance with the invention. For example, whereas the guide inside the piston that prevents the piston from rotating has longitudinal slots receiving pins fixed to the piston, as an alternative the slots can be provided in the piston and the pins can be fixed to the guide. Various alternative lug configurations are also possible. For example instead of having two sets of six lugs on the cylinder and in the receiver, a single set of four lugs on the cylinder and a single set of four lugs in the receiver will allow the head to be set at any of four rotational positions relative to the power unit.
