Abstract:
A battery-powered impact wire insertion tool that employs an electric motor to implement the impacting function. The electric motor is provided with suitable gearing that reduces its speed but increases its torque. An activator mechanism is employed to convert multiple revolutions of the motor shaft into a stored compressive force that after a predetermined number of shaft revolutions is triggered to release the compressive force to drive a hammer against an insertion blade mounted in the tool. The activator mechanism comprises axially-aligned cylindrical end cams with generally complementary surfaces that upon rotation of a driven cam axially extends a follower cam compressing a power compression spring, and upon encountering a cam lobe the driven and follower cams abruptly come together releasing the spring delivering the desired impact to the blade.

Description:
This invention relates to a power wire insertion impact tool, and in particular to a battery-powered tool adapted for insertion of conductor wire in connector blocks and the like. 
     BACKGROUND OF THE INVENTION 
     Wire insertion manual impact tools are well known in the art and are commonly used nowadays for the making of connections to terminals on connector blocks in the electronic and telecommunication fields. See, for example, U.S. Pat. No. 4,241,496, whose contents are herein incorporated by reference, as an example of such tools. 
     Such tools often use an operating mechanism in which a hammer is biased by a compression coil spring to tilt the hammer or another element with respect to the longitudinal axis of the tool. When the hammer or other element is aligned with the axis, the coil spring is released producing the desired impact. Other tools have used a detent mechanism maintaining a spring-biased hammer until the detent is triggered and the kinetic energy of the hammer is transmitted to a blade and in turn to the wire. 
     Power wire insertion tools are also known. Typically, they are powered by electrical power from a room outlet and employ an electrical solenoid which is operated to provide the desired impact when a trigger is activated. These power tools demand less effort from the user and are often preferred especially when numerous wires have to be inserted. 
     A problem is that such power tools are less likely to be used in the field where no local power source is readily available. Moreover, such solenoid-operated insertion tools are not easily operated by a battery because the solenoid consumes too much electrical power and thus the battery is quickly exhausted. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is an improved impact insertion tool. 
     A further object of the invention is a battery-powered impact insertion tool that consumes less electrical power than the known tools of the solenoid type operated off the common household voltage. 
     Another object of the invention is a battery-powered insertion tool exhibiting a reasonable lifetime before requiring battery recharging. 
     Still another object of the invention is a battery-operated insertion tool that is inexpensive to manufacture. 
     These objects are achieved in accordance with a feature of the present invention by a battery-powered insertion tool that employs an electric motor to implement the impacting function. The electric motor is provided with suitable gearing that reduces its speed but increases its torque. An activator mechanism is employed to convert multiple revolutions of the motor shaft into a stored compressive force that after a predetermined number of shaft revolutions is triggered to release the compressive force to drive a hammer against an insertion blade mounted in the tool. 
     In accordance with a preferred embodiment of the invention, the activator mechanism comprises axially-aligned cylindrical end cams with generally complementary surfaces that upon rotation of one of the cams axially extends the other cam compressing a power compression spring, and upon encountering a cam lobe the cams abruptly come together releasing the spring delivering the desired impact to the blade. 
     Another feature is the addition of an impact-force changing feature in the tool that allows a user to change the impact force between a high and a low value. 
     A further feature is the addition to the tool of means for changing the orientation of the blade during use. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description of a presently preferred embodiment when taken in conjunction with the accompanying drawings wherein: 
     In the drawings: 
     FIG. 1 is a side view of one form of wire impact insertion tool according to the invention; 
     FIG. 2 is a front view of the tool of FIG. 1; 
     FIG. 3 is a partial horizontal cross-sectional view of the tool of FIG. 1 along the line  3 — 3 ; 
     FIG. 4 is a partial vertical cross-sectional view of the tool of FIG. 1 along the line  4 — 4 ; 
     FIG. 5 is a partial schematic view of the activating cam mechanism of the tool of FIG. 1 shown in the position before the tool is operated; 
     FIG. 6 is a view similar to that of FIG. 5 with the cam mechanism shown in the position after the tool is operated but just before the compressed spring is released; 
     FIG. 7 is a partial cross-sectional view showing the force changing mechanism of the tool illustrated in FIG. 1 in its high impact position; 
     FIG. 8 is a partial circuit schematic showing how the motor operates and the blade position is controlled. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An impact insertion tool  10  according to one form of the invention is shown in FIGS. 1-4. It includes a gun-type housing comprising a main body  14  supported on a handle  16 . An electric motor  18  drives a shaft  20  which operates a well known 2-stage, planetary gear system  22  which gears down the motor shaft by a factor of about 40-60:1. The planetary gear system  22  rotates about a longitudinal axis  24 . Its details are conventional and not part of the present invention. The motor  18  is activated by a trigger  30  which when pulled closes a circuit which includes a battery power source  32  at the rear of the handle  16 . The mechanical parts of the switch circuit are shown schematically in FIG. 4 at  34  and are conventional. The electrical schematic will be discussed below. 
     It will be observed that the gun-type tool is similar to the power wire-wrapping tool described in U.S. Pat. No. 6,269,845, whose contents are herein incorporated by reference. The preferred embodiment of the present invention uses a housing, battery compartment, and a motor somewhat similar to that used in the power wrapping tool described in the referenced patent. Since the latter is in mass production, this contributes to the low fabrication costs of the tool of the present invention. 
     Attached to the rotating gear system  22  is an axially-aligned elongated cylindrical element  36  that rotates with the gear system  22  and is journaled between two bushings  38  secured to the housing  14 . A power compression spring  40  of the type usually found in manual impact tools is mounted to the inside of the elongated element  36 , and between it and the standard insertion blade  42  at the gun front is a mechanism that converts the motor shaft rotations into an axial force that compresses the spring  40  from its initial state and then abruptly releases the spring  40  to apply the desired impact force to the blade  42 . This is achieved by two axially-aligned cylindrical cams  44 ,  46  whose facing end surfaces engage and are approximately complementary to one another. The cam  44  nearest the motor and adjacent and engaging the power spring  40  is the follower cam and it is axially-slidable but not rotatable within the elongated cylinder  36 . The follower cam  44  also comprises a shaft  48  that extends forwardly and terminates in an axially-extending slot  50  that is pinned  52  to the front bushing  38  and thus rotatably-fixed to the housing. The slot  50  allows the shaft  48  to move axially but prevents its rotation. The cam  46  furthest from the motor  18  is the driven cam and rotates with the elongated cylinder  36 . As illustrated in FIGS. 5 and 6, the camming surfaces  54 ,  56  are configured so that in the cams rest position (FIG.  5 ), the overall axial length of the two cams is a first minimum value, but when the cams have rotated while engaged nearly one complete revolution, just before reaching a cam lobe  58  (shown in FIG.  6 ), the overall axial length of the two cams is a second maximum value, during which the axially-displaced follower  44  compresses the power spring  40  by an amount substantially equal to the difference in their axial lengths, i.e., the difference between the first and second values. Upon encountering the cam lobe  58 , there is an abrupt reduction in the overall axial cam lengths causing the expanding power spring  40  to drive the follower cam forward and the front surface  60  of the cam shaft  48  acting as a hammer  62  impacts a blade-support mount  62  and the latter in turn transfer its kinetic energy via a punch holder  64  to the blade  42  producing the desired impact. It will be appreciated that in the normal operation, the user presses down on the wire and connector with the blade  42 , the result of which is to push the blade-support mount  62  rearwards a short distance until it engages a shoulder on an inner bushing  64  leaving a small space between the facing surfaces of the blade-support mount  62  and cam shaft  48 . Following the impact, the rest position illustrated in FIGS. 3 and 4 is restored. 
     The configuration of the complementary camming surfaces  54 ,  56  may be described, generally, as a helical surface that expands axially, and the rotation of the driven cam  46  pushes the follower cam  44  to the left in FIG.  5 . When the complementary cam lobes  58  meet, the follower  44  has reached the furthest point of its movement and the spring  40  its maximum compression. The right angle orientation of the camming surfaces (compared to the surface shape just prior to the lobe), means that as soon as the lobes pass one another, the cam  44  is driven forward (to the right) by the spring toward its rest position (FIG.  5 ). Before the cam surfaces can reengage, the shaft end surface  60  impacts the facing blade-support mount  62  surface which drives the punch holder  64  forward finally allowing the camming surfaces to reengage in their rest position. Thus, the impact force is not delivered to the blade via the camming surfaces directly thus minimizing cam wear. 
     Assuming an electric motor with a shaft rotation of 10,600 rpm, at a reducing gear ratio of 50:1, it would require approximately 20 motor shaft rotations to produce one complete revolution of the cams and thus one impact. For a typical 3.6 Volt portable battery of the type conventionally used in power tools, the typical battery should be capable of well over 1500 impacts or wire insertions before requiring recharging. This is satisfactory for field use of such a tool. The time required for the motor to provide the required number of shaft rotations per impact is under 0.25 sec. or less, hardly noticeable to the typical user. 
     A feature of the invention is to provide the user with controllable impact force capability. Just behind the front end of the tool is a rotatable collet  80  with internal screw threads that threadingly engages the fixed front bushing  38  and functions to change the blade impact pressure. It preferably accomplishes this by means of an inwardly extending shoulder  82  that engages an outward extension of the internal bushing  65  which is slidingly mounted on the cam shaft  48  and blade-support mount  62 . The bushing rear  84  engages a needle bearing set  86  (FIG. 4) and is thus coupled to the front cam  46 . When the collet  80  is rotated, its axial position changes and via its coupling to the front cam  46  changes the axial position of the latter. This is illustrated in FIGS. 4 and 7. FIG. 4 shows the position of the collet  80 , the bushing  84  and cams when the collet  80  has been rotated to its low impact force position; FIG. 7 shows the position of the collet  80 , the bushing  65  and cams when the collet has been rotated to its high impact force position. These positions may be marked on the outside of the collet as MIN and MAX. Intermediate positions of the collet  80  will provide impact forces varying continuously between the MIN and MAX values. In the low-impact-force position, the collet  80  and bushing  65  are positioned furthest from the motor, and in its high-impact-force position they are positioned nearest to the motor. Its positioning by the user to MIN position is by rotating the collet CCW (viewed from the front), which moves the cylindrical cams away from the power spring; its repositioning by the user to its MAX position is by rotating the collet CW which moves the cylindrical cams toward the power spring. The first action lengthens the rest position of the power spring and the second action shortens the rest position of the power spring. Since the axial lengthening of the dual cams  44 ,  46  during operation remains the same, the shorter power spring when compressed produces a larger impact force; the longer power spring when compressed produces a smaller impact force. 
     A further feature is to force the blade  42  into its normal rest orientation, either horizontally, or vertically as illustrated in FIG. 3, when the tool completes its insertion operation. This is preferably achieved by automatically stopping the motor  18  when the dual cams have completed one full revolution and the power spring has been released. This is accomplished in a preferred embodiment by means of electronic circuitry and an opto-electronic coupler which senses when the cams have completed one full revolution and opens the circuit and short-circuits the motor windings to immediately stop the motor. A preferred form of the circuit is shown in FIG.  8 . The battery  32  and gun switch  30  are shown at the left. These are connected to a low/high frequency filter  100 , to a discharge resistor  102 , and to an RC circuit  104  whose junction is connected to the S or set terminal of a conventional flip/flop  106  which is powered via its vertical connections to the battery and ground. The R or reset and D or data terminals are connected together to ground. The upper Q-bar (NOT-Q) output is connected to the gate of an SCR  108  via a resistor. The anode and cathode of the SCR are connected across the motor  18  windings. The SCR cathode is also connected in series with a HEXFET switch  110  whose gate is connected to the lower Q output of the flip/flop  106 . An opto-electronic sensor  112  comprises an LED  114  optically coupled to a photo-transistor  116  whose collector is connected via a pull-up resistor to the positive side of the battery. The emitter is grounded. An output signal is taken from the collector and is coupled back to the C or clock input of the flip/flop  106 . The LED and photo-transistor are physically positioned in spaced relation on the housing as shown in FIG. 4. A screw  118  serving as an opaque barrier is mounted on the elongated cylinder  36  and rotates with it. In the rest position of the tool, the optical barrier  118  is positioned just past its blocking position between the LED and photo-transistor; typically, say, 10-40° past the blocking position. 
     Operation is as follows. With the gun switch  30  OPEN, the S input is LOW and Q is also LOW. HEXFET switch  110  is also OFF. The motor has no power. The LED  114  is OFF until the switch  30  is activated. Once the operator activates the switch  30  ON, the LED  114  goes ON. With no barrier  118  present, the photo-transistor  116  is also ON, and its collector is LOW and thus the C input is also LOW. Though Q-bar becomes high, the SCR  108  is also OFF since the HEXFET switch  110  is also OFF. However, when the gun switch  30  closed, a single positive HIGH pulse was transmitted to the S input which flipped the state of the flip/flop  106 , making Q-bar LOW and Q HIGH. This turned ON the HEXFET switch  110  providing motor power which then rotated its shaft. The operator keeps the switch  30  closed until the impact takes place maintaining motor power. After one full rotation of the rotating subassembly  36 , the high-low cam lobes meet and pass, the compressed spring releases producing the desired impact and the optical barrier  118  is interposed between the LED and photo-transistor. The photo-transistor goes OFF, its collector goes HIGH and so does the C input. The flip/flop  106  changes state on the rising C input, its Q output goes LOW turning off the HEXFET switch  110  and the power to the motor, and Q-bar goes HIGH. This turns ON the SCR  108  and the stored energy in the motor&#39;s inductive field is shorted through the ON SCR  108  which acts to electrodynamically brake the motor which brings it to a quick stop, though the optical barrier  118  would have by now coasted past its blocking position and the original conditions are restored including restoring of the flip/flop  106  to its original state. The electrodynamic braking and quick stopping of the motor ensures that the original orientation of the blade is restored. The position of the optical barrier  118  can be adjusted at the factory to ensure that the ending blade orientation is that desired. While the above circuit is preferred and is inexpensively implemented on a small circuit board positioned within the housing  14 , those skilled in the art will recognize that other ways can be used to achieve the stopping of the motor following the impact with the blade oriented at a consistent position relative to the gun housing. 
     This tool has the same adjustable blade orientation feature described in a copending patent application, Ser. No. 09/922,256, filed Aug. 6, 2001, whose contents are herein incorporated by reference, in which the blade  42  has notches  66  on opposite edges allowing the blade to be rotated 180° and seated in either position via the front collet  88 , and in addition a blade-orientation collet  68  with a circumferential slot  70  having detent recesses  72  at opposite slot ends engageable by a spring-loaded ball  74 . The spring is shown at  75 . The collet  68  is rotatably mounted on the punch holder  64  so that it has two stable circumferential positions 90° apart. As a result, the blade can be oriented by the user while mounted during use in one of the two 90° positions, and can also be removed from the punch holder  64 , rotated 180° and remounted, providing versatile use by the user when inserting wires into horizontally or vertically oriented connectors and with the blade positioned to cut off the left or right side of the wire as desired. 
     Among the advantages of the power tool of the invention as described herein are: low battery power consumption extending battery life, ease of operation with minimum user stress, low-cost manufacture, user-adjustable impact force between maximum and minimum values and also continuously adjustable between those maximum and minimum values, no excessive wear of the camming surfaces as they are not in the impact path between the power spring and the hammer, and blade orientation in one of four possible circumferential positions. 
     While the invention has been described in connection with preferred embodiments, it will be understood that modifications thereof within the principles outlined above will be evident to those skilled in the art and thus the invention is not limited to the preferred embodiments but is intended to encompass such modifications. For example only, the continuously adjustable force-controlling collet  80  can be replaced by a bayonet-type mounting which however will typically allow only two impact force positions. As another example, the planetary gear-reduction system could be replaced by a worm gear system to obtain a similar speed reduction; however, this might result in the need for a larger housing which is undesirable.