Abstract:
A power feed attachment that has a coupling structure to couple it to a hand held drill. A double-acting cylinder, which has a piston and a rod, and is fixedly coupled to the coupling structure. A two-position valve assembly is configured for directing a pressurized fluid to the double-acting cylinder. When the two-position valve assembly is in a first position is directs a fluid to a first side of the piston moving the piston to a first position. When the two-position valve assembly is in the second position it directs the pressurized fluid to a second side of the piston to move the piston to a second position. An arm is coupled to the piston. A control mechanism having a housing and a control rod, wherein the control rod is movable within the housing of the control mechanism between an extended position and a retracted position. The control mechanism has a biasing device for biasing the control rod toward the extended position, the control rod being configured to contact the arm to resist movement of the piston toward the second position to thereby control a rate by which the piston is advanced toward the second position. The assembly may also include a four-way two position air piloted valve to control the flow of a fluid to the arm.

Description:
FIELD OF THE INVENTION 
     The present invention relates to power feed attachments for drills and more specifically relates to pneumatically powered feed attachments for drills actuated upon activation of the drill. 
     BACKGROUND OF THE INVENTION 
     It is generally known in the art to provide a power feed or drive attachment for a drill motor. A power feed attachment allows a tool bit, for example a drill bit or countersink, that is coupled to a drill to be driven forward without manual power from the user of the tool. As such, the power feed attachment precisely controls the forward feed rate of the tool bit while the remainder of the drill is maintained in a stationary position relative to a work piece. 
     Generally, however, known power feed attachments have several disadvantages. One main disadvantage of commonly known power feed attachments is the fact that they are return driven by springs. The tool is driven forward by any means and is returned to its originating position by a spring. After many uses, the spring tends to become weak or bind due to dirt and foreign material entering into the return mechanism. The binding of the spring reduces the return power or inhibits return of the power feed attachment. Therefore, tools having these power feed attachments must periodically be removed from their production area to permit their power feed attachment to be repaired and/or cleaned so that the tool bit will return properly at the end of the feed cycle. 
     Additionally, many power feed attachments are coupled to their drills such that the tool&#39;s overall center of gravity is located too far to the front of the power tool, giving the tool an unbalanced, nose-heavy feel. Therefore, when an operator attempts to use the tool strain is placed on the operator&#39;s hands, wrists, and arms during operation making the tool uncomfortable to use. Furthermore, the unbalanced nature of the tool tends to destabilize the tool and inhibits the precision with which the tool may be operated. 
     Furthermore, many power feed attachments add significant additional length to the power tool which tends to reduce its versatility by rendering the tool incapable of use in relatively small places or in awkward positions. With the increased length of the tool, there is no way to mount the tool in small places to allow the power feed attachment to work. 
     Therefore, there has been a long felt need to provide a power feed attachment that reduces the above-mentioned disadvantages among others. In particular, a power feed attachment would generally be more useful if it were compact so that a tool may be used in many different locations, including small or cramped ones, and in awkward positions. Furthermore, it is desirable to include a power feed attachment that does not place the center of gravity away from the user&#39;s hands or the grip of the power tool. Therefore, the tool would be easier to maneuver and its position more accurately maintained relative to the work piece during the tool&#39;s operation. Finally, it has generally been felt that a simple and highly efficient power feed attachment is needed. Also, a power feed attachment that does not require special parts or mechanisms thereby reducing cost and repair time. One where there are fewer parts that require maintenance and a power source that can easily overpower any foreign material or grime that may build up within the mechanism with general use. The power feed attachment would also need to be driven and retract upon a signal from the tool depending upon whether it is being driven or not. 
     SUMMARY OF THE INVENTION 
     The present invention provides a power feed attachment for a drill motor which is designed so that the drill motor may be used in numerous orientations. The compactness of the attachment also allows it to be used in tight places where large tools cannot easily access. The present invention, however, does not sacrifice power, but rather increases return power over other attachments. 
     Additionally, the present invention provides a power feed attachment that has a simplified and more durable mechanism. Maintenance and downtime may be reduced due to the long-term durability of the present invention. Additionally, the mechanism of the present invention does not use parts or systems that are easily inhibited by the dust, dirt, chips, and grime that is encountered in general shop or working conditions. The system of the present invention provides enough power to the power feed attachment that foreign material introduced to the apparatus will not effect the operation of the present invention. 
     The power feed attachment of the present invention allows for very precisely drilled holes and countersink tolerances. The present invention provides systems that finely control the feed rate of the power feed attachment thereby allowing precise drill holes and countersinks without a great deal of effort from the operator of the power tool. 
     Additionally, the mechanism of the present invention is easily maintained and serviced. Rather than requiring numerous intricate parts, the present invention provides an apparatus which is produced from several large easily replaceable parts which comprise the system of the present invention. Therefore, even if maintenance is required on the present invention, the maintenance is easily performed and advantageous to a continuation of the production schedule. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a side elevational view of a power tool having a power feed attachment disposed in an extended position and constructed in accordance with the teachings of a first embodiment of the present invention; 
     FIG. 2 is a front perspective view of the power tool of FIG. 1; 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a side elevational view of the power tool of FIG. 1 illustrating the power tool engaged to a work piece and the power feed attachment disposed in a retracted position; 
     FIG. 5 is a side elevational view of a power tool having a power feed attachment constructed in accordance with the teachings of a second embodiment of the present invention; and 
     FIG. 6 is a front perspective view of the power tool of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     With reference to FIG. 1 of the drawings, a power tool assembly  10  is illustrated to include a power feed attachment  12 , which is constructed in accordance with the teachings of the present invention, and a power tool, which, in the example provided, is a drill motor  14 . The drill motor  14  generally includes a pistol grip  16  affixed to a motor casing  18 . Motor casing  18  encloses a motor (not shown), which is activated by pressing trigger  20 . Activation of the motor conventionally rotates the spindle  22 , and the chuck  24 , and, when affixed within the chuck  24 , a tool bit  26 . Tool bit  26  may be any appropriate tool bit  26  including a drill bit or a countersink bit. Affixed to the pistol grip  16  and extending from an end opposite motor casing  18  is a male coupling  28  which connects to a female coupling  30  of a fluid supply hose  32  extending from a power source  33 . In particular, the fluid supplied to the drill motor  14  is compressed air. 
     With additional reference to FIGS. 1-4, the power feed attachment  12  is shown to generally include a double acting air cylinder  36 . Double acting air cylinder  36  may be any conventional double acting air cylinder, such as a 01 Series Micro-Air Cylinder, Part No. 0118-5029-010, manufactured by the ARO Corporation. Double acting air cylinder  36  includes an air driven piston  38 , having a first side  38   a  and a second side  38   b , and a first piston rod  40 , coupled to air driven piston  38 , that extends from a front portion  36   a  of double acting air cylinder  36 . First piston rod  40  engages an intermediate or connection member  42  through a threaded portion  43  at a forward end  40   a  of first piston rod  40  and a rearward end  42   a  of connection member  42 . Furthermore, a forward end  42   b  of connection member  42  includes threads  42   c  which engage a forward or guide arm  44  of power feed attachment  12 . Affixed to guide arm  44  is a bushing  46 . Guide arm  44  and bushing  46  act to guide tool bit  26  during the actuation of drill motor  14 . Bushing  46  may be affixed to guide arm  44  through any suitable means and is shown to be clamped between two portions of guide arm  44  and affixed in place with a screw  48 . Bushing  46  may be any conventional bushing which may be affixed to a drill plate of or other appropriate structure. Many bushings are available to interact with different drill plates and a proper bushing may be chosen depending upon the application. A resilient member  45 , which may be formed of any suitable material, may be affixed around bushing  46 , and extend in front of bushing  46 , to allow a press fit onto the workpiece. According to the present embodiment resilient member  45  is formed of a polymer material to reduce movement of the power tool assembly  10  during use. First piston rod  40 , connection member  42  and guide arm  44  all slideably move within a casing or housing  50 . It is to be understood that the embodiment described herein is merely exemplary, and as such, those skilled in the art will readily understand that the three portions, first piston rod  40 , connection member  42 , and guide arm  44  may all be one piece. Furthermore, connections between the various portions may be by any suitable means. Double acting air cylinder  36  may engage housing  50  either indirectly or directly, as through a secondary threading housing  52 . Furthermore, the double acting air cylinder  36 , guide arm  44 , and bushing  46  are oriented generally in line with one another. Furthermore, not only are the separate components inline with one another, but in the same general plane over casing  18  of drill motor  14 . This alignment assists in reducing binding and increasing accuracy of tool bit  26  into a work piece (described herein). Forces are linear as opposed to being applied off center or out of line. The incidence of binding and maintenance due to misalignment is reduced. Due to the reduced binding and increased accuracy tool maintenance is greatly reduced. 
     Power feed attachment  12  also includes a control system  56  including a hydraulic cylinder  58  having a front end  58   a  with a front portion  59  of a second piston rod  60  extending therefrom. Control system  56  also includes a variable connection or attachment  62  that couples second piston rod  60  to guide arm  44 . Hydraulic cylinder  58  may be any suitable hydraulic cylinder such as a Slimline Kineschek Feed Control Part No. 1002-31-1 manufactured by Deschner Corporation. Front portion  59  of piston rod  60  engages guide arm  44  through variable attachment  62 . Variable attachment  62  includes a threaded bore  63  which receives front portion  59  of second piston rod  60 . Front portion  59  of second piston rod  60  engages a set screw  64 . Set screw  64  is received in threaded bore  63  and may be adjusted in and out of threaded bore  63  to adjust the effective length of second piston rod  60 . A nut  66  engages set screw  64  and acts as a jamb nut against variable attachment  62  to hold set screw  64  at the desired position. A rear side  67  of variable attachment  62  engages nut  66  forming a datum surface. As described herein, when power feed attachment  12  is activated, guide arm  44  is drawn towards chuck  24  in the direction of Arrow A. As also described herein, control system  56  controls the rate of movement of guide arm  44  by engaging variable attachment  62  with set screw  64 . Set screw  64  may be adjusted rearwardly or forwardly in threaded bore  63  to adjust the distance of retraction depending upon the application in which the power tool assembly  10  will be used. An adjustment screw  68  allows a varying resistance to be produced by hydraulic cylinder  58 . Adjustment screw  68  allows resistance produced by hydraulic cylinder  58  to be adjusted so that rate of the retraction of power feed attachment  12  may be precisely controlled. 
     Affixed next to housing  50  of the power feed attachment  12  is a valve  72 . Valve  72  may be any suitable 2-position valve with a spring return such as an Eagle 4-way Valve Part No. E4-1PS00-000 manufactured by the Clippard Instrument Laboratory, Inc. Valve  72  includes a first inlet  74  and a second inlet  76  while also including a first outlet  78  and a second outlet  80 . A first inlet line  82  connects the male coupling  28  through a first bore  84  created therein, to first inlet  74 . First inlet line  82  may be affixed to first bore  84  through any suitable means capable of being sealed to the fluid. A second inlet line  86  connects a second bore  88  formed in motor casing  18  to second inlet  76 . Second bore  88  in motor casing  18  is drilled through the outside cast wall of motor casing  18 . Second bore  88  reaches an internal cavity (not shown) that becomes pressurized when trigger  20  is pressed. Again, second inlet line  86  may be affixed to second bore  88  through any suitable means that is substantially sealed to the fluid. A first outlet drive line  90  connects first outlet  78  and a rear portion  91  of double acting air cylinder  36 . A second outlet drive line  92  connects a front portion  36   a  of double acting air cylinder  36  to second outlet  80 . First outlet drive line  90  provides fluid to a first side  38   a  of air driven air driven piston  38  while second outlet drive line  92  provides fluid to a second side  38   b  of air driven air driven piston  38 . 
     Power feed attachment  12  may be affixed to drill motor  14  through any suitable means. As an example, yoke or clamp portion  94  extends from housing  50  and wraps around motor casing  18  and is held in place by a screw  96 . Any other means, however, may affix power feed attachment  12  to drill motor  14  making power feed attachment  12  a universal attachment to any suitable tool. 
     Drill motor  14  is a pneumatic powered drill. Pressurized air is received through male coupling  28  and then travels through the tool to power the motor to rotate chuck  24 . Due to this fact, male coupling  28  is constantly powered or pressurized by the air coming from power source  33 . Therefore, first inlet line  82  provides a constant source of pressurized air or power to valve  72  of power feed attachment  12 . Valve  72  is biased in a first position by an internal biasing spring (not shown), allowing the constant pressure of air provided through first inlet line  82  to travel through valve  72  out first outlet drive line  90  to rear portion  36   b  of double acting air cylinder  36 . Since this is the biased or normal position of valve  72 , air is constantly supplied to the back of double acting air cylinder  36  therefore driving air driven piston  38  to an extended or forward position, as shown in FIGS. 1-3. In turn, this maintains guide arm  44  in a forward position, which is distal from chuck  24 , and bushing  46  at a maximum allowable distance from chuck  24 . 
     When an operator of the drill motor  14  presses trigger  20 , air is then allowed to travel to motor casing  18  to power the motor. When air enters motor casing  18 , air also pressurizes second inlet line  86  through second bore  88 . Second bore  88  in the motor casing  18  allows air to travel out of motor casing to provide a signal to valve  72 . The signal provided when trigger  20  is pressed moves valve  72  to a second position. In the second position, valve  72  transfers the pressurized air from power source  33  from first outlet drive line  90  to second outlet drive line  92 . When this occurs, the second side  36   b  of double acting air cylinder  36  and also the second side  38   b  of air driven air driven piston  38  becomes pressurized driving air driven piston  38  in a second, rearward, or retracted position towards the rear portion  36   a  of double acting air cylinder  36  as shown in FIG.  4 . Therefore, the activated position of the power tool assembly  10  is the retracted position as shown in FIG.  4 . In particular, the retracted position moves bushing  46  in the direction of Arrow A to dispose bushing  46  nearer chuck  24 . If power feed attachment  12  includes no controlling mechanisms the movement from the extended to the retracted position would be almost instantaneous. Since the air pressure is simply diverted from first side  38   a  to second side  38   b  of air driven piston  38  allowing guide arm  44  to retract toward chuck  24  as rapidly as the pressure of the air allows. 
     Control system  56  controls the rate of retraction of guide arm  44 . In particular, hydraulic cylinder  58 , of control system  56 , provides hydraulic resistance through second piston rod  60  and variable attachment  62 . As guide arm  44  is drawn towards chuck  24  guide arm  44  interacts with hydraulic cylinder  58 . The resistance in hydraulic cylinder  58  controls the retraction of guide arm  44  towards chuck  24 . Set screw  64  may also be adjusted to determine the distance of retraction of guide arm  44  towards chuck  24 . Moving set screw  64  in threaded bore  63 , changes the effective length of second piston rod  60 . If set screw  64  is made to decrease the effective length of second piston rod  60  then there is less distance for the piston to travel in hydraulic cylinder  58  thereby decreasing the distance that guide arm  44  may travel. Additionally, adjustment screw  68  allows the resistance produced by hydraulic cylinder  58  of control system  56  to be adjusted. Increasing the resistance created by hydraulic cylinder  58 , decreases the rate of the retraction of guide arm  44  towards chuck  24 . Whereas, reducing the resistance of hydraulic cylinder  58  increases the retraction rate of guide arm  44  towards chuck  24 . Various applications require differing rates of feed of bit  26  through the work piece W. 
     Adjustment of set screw  64  also allows for a precise depth of tool bit  26  into work piece W. Therefore, a continuous and easily repeated rate and depth of tool bit  26  into work piece W is reproduced by simply adjusting the set screw  64  and the adjustment screw  68  of power feed attachment  12 . 
     Generally, the bushing  46  will be affixed to the work piece W by any appropriate means. In one embodiment, the outer diameter of the bushing  46  would mate substantially well with an inner diameter ID of a hole in an outer work piece or drill plate D thereby creating enough friction to hold power tool assembly  10  in a friction fit between the bushing  46  and drill plate D through which the tool bit  26  is to be driven. It is understood that drill motor  14  is driven towards the work piece W when guide arm  44  is retracted towards chuck  24 . In this way, the precise depth and rate of the tool bit  26  into work piece W is obtained. Resilient member  45  may be used in place of the friction fit for a press fit attachment. Drill motor  14  is still drawn towards workpiece W, but is held in place by resilient member  45 . 
     During the drilling operation the operator of the power tool assembly  10  moves the power tool assembly  10  through a feed cycle. The feed cycle includes an extended position to retracted position to extended position action. Power feed attachment  12  performs the entire cycle while the operator has to hold the drill motor  14  and operate trigger  20 . Once guide arm  44  has retracted enough towards chuck  24 , second piston rod  60  has reached a maximum retraction travel distance, bushing  46  and guide arm  44  stop the travel towards the retracted position. When the retracted motion has stopped the operator of the power tool assembly  10  releases trigger  20 . When trigger  20  has been released motor casing  18  is no longer pressurized with air from power source  33 . Therefore, second bore  88  is also not pressurized thus removing pressure from second inlet line  86  and allowing the spring in valve  72  to bias valve  72  in the first position. When valve  72  is biased in the first position, air from power source  33  travels through first inlet line  82  and out first outlet drive line  90  to pressurize first side  38   a  of air driven piston  38 . This drives air driven piston  38  towards front portion  36   a  of double acting air cylinder  36  and drives guide arm  44  towards the extended position. In this way, double acting air cylinder  36  provides pneumatic power to move power feed attachment  12  between the retracted and extended positions. The pneumatic power provided by double acting air cylinder  36  helps insure that enough power is provided for extended usage and reduced maintenance or cleanings of the present invention. In particular, the pneumatic power provided to double acting air cylinder  36  provides enough power or force to overcome most general resistances which may form in double acting air cylinder  36  due to foreign materials entering the cylinder or foreign materials entering the housing  50 . 
     The control system  56  also allows for an easily repeatable rate of retraction. Once the retraction rate has been set using hydraulic cylinder  58  and adjusting the resistance with adjustment screw  68  power tool assembly  10  will always advance to that rate that has been chosen. Therefore, power feed attachment  12  may be adjusted to provide a repeatable predetermined rate of retraction allowing that rate to be applied to the guide arm  44  to move power tool assembly  10 . Additionally, the use of variable attachments  62  and second piston rod  60  allows for an easily repeatable depth of tool bit  26  into work piece W. Therefore, the operation of the power tool assembly  10  is easily repeatable without much control being necessary from an operator. For exemplary purposes only a repeatable countersink variance achieved was about 0.0015 inches in hole diameter and 0.007 inches in countersink diameter, when a counter sink was the tool bit  26  used. Also as an example, a Cp of about 1.61 has been achieved with this embodiment if a drill bit is chosen as the tool bit  26 . 
     With reference to FIGS. 5 and 6, a second embodiment of the present invention is shown where like elements are given like numerals. The drill motor  14  and its associated parts are similar to those of the first embodiment discussed above, also similar portions of power feed attachment  12  will not be repeated. In the second embodiment, a coolant valve  200  is also included. The coolant valve  200  may be any appropriate 2-position valve but is preferably a pilot-operated valve, such as an Eagle 4-way valve, Part No. E4-1PP-00-000 manufactured by the Clippard Instrument Laboratory, Inc. Coolant valve  200  includes a coolant inlet  202  and a coolant outlet  204 . A coolant inlet line  206  connects a coolant supply  207  and coolant inlet  202  of coolant valve  200 . A coolant outlet line  208  connects coolant outlet  204  and a bushing  210 . Bushing  210  is similar to bushing  46 , discussed in relation to the first embodiment, except that it is able to receive coolant from the coolant outlet line  208  to provide cooling to the work piece or tool bit  26  during operation. In this way, harder materials may be drilled without overheating the work piece or tool bit  26  causing damage to both. Coolant valve  200  also includes a first power inlet  212  and a second power inlet  214 . A first inlet line  216  operatively connects first power inlet  212  of valve  200  with first drive outlet line  213 . A second inlet line  218  operatively interconnects second power inlet  214  with second drive outlet line  215 . 
     Coolant valve  200  selectively allows coolant to flow from the coolant supply  207  to bushing  210  depending upon the state of drill motor  14 . When drill motor  14  is not activated, first drive outlet line  213  is pressurized, as discussed above in relation to first drive outlet line  90 . First inlet line  216  is also pressurized, biasing coolant valve  200  in a closed position so that coolant is not allowed to flow through coolant valve  200  to bushing  210 . However, when drill motor  14  is activated, second drive outlet line  215  becomes pressurized, as discussed above in relation to second drive outlet line  92 , causing coolant valve  200  to move to an open position to permit coolant to flow to bushing  210 . Coolant is only allowed to flow through coolant valve  200  when drill motor  14  is activated and as such, a constant supply of coolant may be supplied to coolant valve  200  and to drill motor  14  for operation, without concerns for manually switching on and off a coolant flow. Advantageously, this ensures that a coolant flow is present when one is necessary. 
     Valve  200  is operated to move between both the open and the closed positions through pneumatic power provided by signals from drive outlet lines  213 ,  215 . Coolant valve  200  is not spring biased in either direction. Coolant valve  200  is therefore able to overcome materials and coolant that may bind coolant valve  200  during normal operation. The power provided through inlets  212 ,  214  provide the power for switching the coolant valve  200  between the open and closed positions thus ensuring enough power for ease of operation is provided and to reduce repair or cleaning occurrence of coolant valve  200  to ensure proper operation. The mechanism of the second embodiment is otherwise identical to that described with the first embodiment in regards to the control of the rate and depth by which tool bit  26  is advanced toward a work piece. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.