HAND-HELD POWER TOOL WITH ON/OFF SWITCH IN REAR PART OF ERGONOMIC HANDLE

Abstract: A hand-held power tool (10) with a front end for urging in a forward direction with a power takeoff (20) at the front end rotatable about an axis (40) and a handle (48) for grasping by a hand of the user disposed at an acute angle (42) to the axis (48). A downwardly directed support surface (74) above the handle (48) for engagement by upper surfaces of a hand of user to assist in supporting the tool (10) preferably with the support surface (74) above the axis (40) and an on/off switch (50) activatable by pressure from the palm of a user's hand urging the tool into the workpiece (66).

Description: HAND HELD POWER TOOL WITH ON/OFF SWITCH IN REAR PART OF ERGONOMIC HANDLE Field Of The Invention This invention relates to hand held power tools and, particularly, to hand held screwguns and hand held drills. Background Of The Invention Hand held power tools are well known. Typical power drills and power screwguns have a handle which extends downwardly and from the rear of a drive motor. The drive motor rotates about an axis substantially perpendicular to the handle and with the front end of the drive motor being coupled as to a chuck for holding drills or to a screw bit which rotates parallel the axis of the drive motor. Such power tools have the disadvantage that the weight of the motor is forward of the handle and must be supported by the strength of a user's hand manually holding the tool. Screwdriving apparatus are known for collated screws. Typical apparatus of this type are illustrated, for example, in U.S. Patent 3,930,297 to Potucek et al, issued January 6, 1976, U.S. Patent 5,027,679 to Kawashima et al, issued July 2, 1991 and U.S. Patent 5,186,085 to Monacelli, issued February 16, 1993. Each of these patents show a power screwgun having a handle rearward of the motor and extending downwardly therefrom and an attachment coupled to the front of the screwgun which is adapted to feed collated screws in a manner that successive screws may be driven on the tool being successively urged forwardly into a workpiece. Preferred attachment for such devices is shown in U.S. Patent 4,146,071 to Mueller et al, issued March 27, 1979 and U.S. Patent 5,568,753 to Habermehl et al, issued October 29, 1996. A disadvantage of power tools generally with a handle rearward of the motor and particularly of such devices when used for driving collated screws is that the handle is distanced from the workpiece to be engaged which causes difficulty in control as well as increased weight to be supported by the hand of a user. U.S. Patent 4,623,597 to Cast issued December 2, 1986 and U.S. Patent 5, 109,738 to Farian et al, issued May 5, 1992, teach collated screwdriving apparatus in which a handle extends perpendicularly from the axis of a motor and is located under the motor, that is, forwardly from the rear of the motor. These devices while, to some extent, overcome the difficulties of having the substantial weight of the tool forward of the handle, continue to have the disadvantage of resulting in a large tool and with the substantial weight of the motor supported above the handle and in the way of a user of the tool. Another disadvantage of known hand held power tools, such as typical power drills and screwguns, is that a trigger switch is provided on a forward end of the handle which trigger switch must be drawn towards the handle by the fingers of a user in order to operate the tool. This has the disadvantage of being tiring to a user when a tool is used for an extended period of time. Some tools are provided with a locking mechanism which permits the trigger to be locked in an operative position, however, this has the disadvantage of being unsafe in certain circumstances. Summary Of The Invention To at least partially overcome some of these disadvantages of the previously known devices, the present invention provides a power tool with a power drive train extending internally within a housing from a motor disposed near one end of the housing to a power takeoff at the other end of the housing such that the power train extends through an intermediate handle- forming portion of the housing adapted to be grasped by a hand of the user. To at least partially overcome the disadvantages of the prior art, the present invention also provides a power operated hand tool adapted for use by urging the tool manually into a workpiece in which an on/off switch for the tool is activatable by pressure from the palm of a user's hand urging the tool into the workpiece. An object of the present invention is to provide hand held power tools with a handle between a drive motor and the power takeoff from the tool. Another object is to provide a hand tool in which the handle is disposed proximate the center of gravity of the tool. Another object is to provide a hand tool in which the motor rotates about a motor axis disposed at a substantial angle to the axis about which the power takeoff rotates. Another object is to provide a compact lightweight arrangement for a hand held screwdriving gun for automatic advancing and driving of collated screws. Another object is to provide a hand held power tool with an on/off switch which is operative by pressure from a user's hand urging the tool into a workpiece. Another object is to provide a hand tool with an on/off switch provided on a rear portion of a handle. Another object is to provide an on/off switch on a power hand tool for operation by engagement with the palm of a user's hand. Another object is to provide a tool which has a support surface to be engaged by upper surfaces of a user's hand to support the tool. Another object is to provide a tool and, particularly, a balanced tool which assists in reducing hand and arm fatigue in use. Another object is to provide a tool and, preferably, a tool for driving collated screws which has its mass generally symmetrical about a central vertical plane passing through the tool centrally of a handle for the tool. Accordingly, in a first aspect, the present invention provides a hand held power tool with a power drive train extending externally within an elongate housing from a motor disposed near one end of the housing through a handle-forming intermediate portion of the housing to a power takeoff at another end of the housing, wherein the fingers and hand of a user grasp the handle-forming portion to substantially encircle a section of the power drive train passing through the handle-forming portion. In a second aspect, the present invention provides in a power operated hand tool adapted for use by urging the tool manually into a workpiece, the improvement wherein an on/off switch for the tool is activatable by pressure from the palm of a user's hand urging the tool into the workpiece. In a third aspect, the present invention provides a power operated hand tool having a front end for urging in a forward direction into a workpiece, a handle for grasping by the hand of a user, a rear surface portion provided on a side of the handle opposite to the front end for engagement by a portion of the palm of a user's hand; a switch for switching the tool between an inoperative condition and an operative condition, the switch carried on the rear surface portion of the handle and movable between an extended position in which the switch extends rearwardly from the handle and a retracted operative position in which the switch is retracted forwardly into the handle, the switch biased for movement towards the rearward extended inoperative position, wherein on a user's hand grasping the handle of the tool and urging the tool forwardly into a workpiece, the switch is urged by the palm of the hand into the operative retracted position. In a fourth aspect, the present invention provides a power operated hand tool comprising: a front end for urging in a forward direction into a workpiece; a power takeoff at the front end rotatable about an axis; a handle for grasping by a hand of a user; the handle disposed at an acute angle to the axis and having a rearwardly directed rear surface and two opposed side surfaces extending forwardly from the rear surface; a downwardly directed support surface above the handle extending in a forward and rearward direction roughly parallel to the axis; the support surface located above the axis such that a rearward extension of the axis intersects the rear surface below the support surface; the support surface extending sidewardly from each side surface and/or rearwardly from the rear surface for engagement by upper surfaces of an index finger and a thumb of a user's hand when grasping the handle with the palm of the user engaging the rear surface, the fingers extending forwardly from the rear surface on one side surface and the thumb extending forwardly from the rear surface on the other side surface. Brief Description Of The Drawings Further aspects and advantages of the present application will become apparent from the following description taken together with the accompanying drawings and in which: Figure 1 is a side view of a first prefeπed embodiment of a hand held screwgun in accordance with the present invention shown grasped in the hand of a user and positioned to drive a screw into a workpiece with a bit; Figures 2, 3 and 4 are, respectively, front view, a top view and a rear view of the screwgun of Figure 1 ; Figure 5 is a side view of the screwgun of Figure 1 but schematically illustrating internal functional features; Figure 6 is a side view of the screwgun of Figures 1 to 4 but with a driver attachment secured for receiving, advancing and locating collated screws to be driven; Figure 7 is a side view of a power drill similar to the screwgun of Figures 1 to 5; Figure 8 is a side view of a second embodiment of a hand held power tool in accordance with the present invention; Figure 9 is a rear view of the tool of Figure 8; Figure 10 is a side view of a third embodiment of a hand held power tool in accordance with the present invention, and; Figure 11 is a rear view of the tool of Figure 10. Detailed Description Of The Drawings Reference is made to Figures 1 to 5 which show a preferred embodiment of a screwgun 10 having a housing generally indicated as 12. Figure 5 comprises a side view and in which there are schematically shown in dotted lines a number of the functional elements of the screwgun 10 disposed within the housing 12. In this regard, Figure 5 shows a motor 14 rotatable about a motor axis 16. The motor 14 is connected via a transmission mechanism generally indicated 18 to a power takeoff mechanism generally indicated 20. The takeoff mechanism in the prefeπed embodiment is shown as comprising a hex coupling 22 adapted in a known manner to removably receive coaxially within its hexagonal bore 24 conventional screwdriver bits and mandrels having a coπesponding hexagonal outer surface. The takeoff mechanism 20 in a conventional screwgun will also have a clutch mechanism which will permit the screwdriver bit being driven to stop rotating when the resistance to rotation of the bit, as when a screw is fully engaged into a workpiece, increases above a certain desired amount. In this regard, the takeoff mechanism is schematically shown as having two friction clutch plates 26 and 28 serving as a clutch mechanism. The transmission mechanism generally indicated 18 which couples the takeoff mechanism 20 to the motor 14 is schematically shown as comprising a first shaft 30 coupled at one end to the motor and carrying a first bevel gear 32 rotatable therewith. The first bevel gear 32 engages with a second bevel gear 34 which is carried on a shaft 34 coupled via the clutch plates 26 and 28 of the clutch mechanism to the hex coupling 22. As shown in Figure 1 , the motor 14 rotates about the motor axis 16 and the takeoff mechanism 20 and, particularly the hex coupling 22, rotates about a takeoff axis 40. In the prefeπed embodiment, the motor axis 16 and the takeoff axis 40 both lie in the same flat plane. The motor axis 16 and the takeoff axis 40 are both shown in Figure 2 and the flat plane in which both the axis are prefeπed to lie is to be understood to extend normal to the plane of Figure 2. As seen in Figure 5, the motor axis 16 and takeoff axis 40 form an angle indicated generally as 42 which angle is preferably in the range of 20° to 65° and, more preferably, in the range of about 35° to 55° and, most preferably, about 45°. The housing 12 is somewhat elongated and includes three portions. A first housing portion 44 is provided as a lowermost first rear end portion of the housing within which the motor 14 is disposed. A second housing portion 46 comprises a second uppermost forward end portion of the housing at the opposite end of the housing to the first portion 44 and within which the takeoff mechanism 20 is provided. An intermediate handle-forming portion 48 is provided inbetween the first housing portion 44 and the second housing portion 46. The transmission mechanism 18 extends internally of the housing 12 between the motor 14 and the takeoff mechanism 20 and, therefore, internally through the intermediate handle-forming housing portion 48. The intermediate handle-forming portion is disposed at an angle to the axis 40. The intermediate housing portion 48 is shaped so as to permit manual grasping of the screwgun 10 by the hand of a user as shown in Figure 5. In the preferred screwgun 10 shown, the intermediate housing portion 48 is provided of a circumference which is less than the circumference of the first housing portion 44 and it is to be appreciated that the present invention is particularly adapted for use with power tools in which the motor 44 requires a motor receiving first housing portion 44 which is of a circumference which is greater than the circumference of a conventional pistol grip type handle which can be used by a typical person. The intermediate housing portion 48 is shaped for grasping by a user with the hand, fingers and thumb of a user to substantially encircle the intermediate housing portion 48. Nevertheless, the intermediate housing portion 48 is adapted to permit the transmission mechanism 18 to pass essentially therethrough and, therefore, in effect, with the hand, fingers and thumb of the user to substantially encircle the first shaft 30 comprising a portion of the transmission mechanism 18. Figure 5 also schematically shows a switch mechanism including a switch 50 to switch the power on or off to the motor and thus switch the screwgun between a powered operative condition and an unpowered inoperative condition. The switch mechanism is only schematically illustrated by the switch 50 which is disposed in a slot generally indicated 52 in a rearwardly directed rear surface 54 ofthe intermediate handle-forming portion 48. The switch 50 is shown schematically as a generally rectangular rod which is secured to the housing by a pivot pin 56 and is pivotable about pin 56. A spring, schematically shown as 58 in broken lines in Figure 1, is coiled about the pivot pin 56 and has one end secured to the housing and the other end secured to the switch 50 so as to bias the switch 50 clockwise about the pivot pin 56 as seen in Figure 5 to an extended, inoperative position, which inoperative position is shown in Figures 1 to 5 with rear surfaces 60 of the switch in solid lines. The switch may pivot about the pivot pin 56 against the bias of the spring 58 to a retracted position indicated by the switch as shown totally in dashed and dotted lines in Figure 1 and assuming a position as identified by reference numeral 50a. With the switch 50 in the retracted position, the switch mechanism connects the power to the motor and the tool is in an operative condition. Stop mechanisms, not shown, are provided to limit the forward and rearward extent to which the switch 50 may pivot. Reference is now made to Figure 1 which shows the screwgun 10 with a bit 62 received in the hex coupling 14, a screw 64 engaged by the bit and aligned for driving into a workpiece schematically illustrated as 66. The tool as shown being grasped by the hand of a user generally indicated 68. To drive the screw 64 into the workpiece, the hand of the user, which grasps the handle so as to substantially encircle the handle, urges the entire tool into the workpiece in a forward direction parallel the takeoff axis 40. In urging the front end of the tool forwardly towards the workpiece along takeoff axis 40, the palm of the hand is disposed to engage the rear surface 60 of the switch 50 and, on urging of the tool forwardly into the workpiece, urges the switch 50 forwardly to pivot from the inoperative extended position to the operative retracted position. In a person driving a screw, relatively substantial forces need to be applied by the hand of the user onto the rear surfaces 60 of the intermediate handle-forming portion 48 of the housing. Such forces also serve the purpose of maintaining the switch 50 in the retracted operative condition without the need for pressure to be applied to the switch 50 as by the fingers of the user's hand exerting pressure on the forward surfaces 72 of the intermediate handle-forming portion 48. Operation of the tool with the switch 50 engaged by the palm of the hand in the hand urging the tool into the workpiece, permits the tool to be held relatively loosely in the hand of the user without the need for the fingers apply a rearwardly directed pressure onto the forward surfaces of the tool to maintain the switch in an operative condition. In contrast, power tools having a trigger switch forward of the handle typically require such rearwardly directed finger pressure. The switch mechanism is readily operated by the rearward pressure of the palm of a hand onto the rear surfaces of the handle-forming housing portion 48. The switch 50 illustrated in Figures 1 to 7 comprises a mechanically activated switch on the rear surface 54 of the handle. While a mechanical switch, which is pivoted at its lower end is illustrated, many other forms of mechanical switches may be used which are activated by rearward pressure. Preferably, the mechanical switch would engage sufficient area of the palm and/or require such pressure for activation, that discomfort would not be experienced by a user even when using the tool for an extended period of time. Rather than use a mechanical switch, other switches such as an electronic pressure sensing member could be provided on the rear surface 60 in substitution of switch 50. Such plates are believed to be used in elevators and other devices and have no moving parts. The electronic pressure sensing member could be provided flush with the rear surfaces in the area of where the slot 52 is now provided to accommodate the mechanical switch. As seen in Figure 1, portions of the wrist 70 and forearm 72 of a user are shown to extend rearwardly from the tool and, preferably, substantially parallel the takeoff axis 40 as is advantageous for urging the screwgun into a workpiece. In this regard, with the hand 68 of the user grasping the tool, the takeoff axis is seen to extend rearwardly and conceptually intersect with the palm of the user. The screwgun 10 is provided with a support mechanism 74 comprising a plate 73 comprising a part of or secured to the housing above and adjacent the intermediate handle-forming portion 48 and which plate provides a substantially, downwardly directed, flat planar support surface 76 which extends in a forward and rearward direction roughly parallel to axis 40 and which is adapted to be engaged by the upper surface of the hand and wrist and, particularly, the upper surface of the thumb 84 and the rear of the index finger as well as portions of the hand and wrist rearward from the thumb and index finger as best seen in Figure 1. The support surface 76 extends both to the sides and rearwardly of the handle-forming housing portion 48. In this regard, the handle-forming housing portion 48 has a rearwardly directed rear surface 54 and two opposed side surfaces 53 and 55 extending forwardly from rear surface 54. The support surface 76 is located above axis 40 such that a rearward extension of axis 40 intersects the rear surface 54 below the support surface 76. The support surface 76 extends sideways from each side surface 53 and 55 and rearwardly from the rear surface 54 for engagement by upper surfaces of an index finger and a thumb of a user's hand when grasping the handle-forming housing portion 48 with the palm of the user engaging the rear surface 54, the finger extending forwardly from the rear surface 54 on one side surface 53 and the thumb extending forwardly from the rear surface 54 on the other side surface 55. As seen, the support surface 76 extends sideways and rearwardly from the rear and side surfaces of the handle-forming housing portion 48 beyond the the thickness of a normal finger of a user. The tool may be seen to be symmetrical in a flat plane in which the axis 40 lies and the support surface 76 is normal to this flat plane. The support surface 76 also forms, as seen in Figure 1 , with the remainder of the rear surface 54 of the handle- forming portion 48, a U- shaped bight whose center is forwardly directed. This is advantageous such that on a user urging the tool into a workpiece with the hand, the hand will effectively be cammed and biased by the U-shaped bight towards a central alignment in the U-shaped bight which will assist in reducing the extent to which the fingers of the hand must apply rearwardly directed pressure to the handle of the tool to secure and hold the tool. In the configuration of the hand shown in Figure 1 , the fingers as they initially extend from the palm of the hand are generally directed in a direction parallel the takeoff axis 40 as is believed to be advantageous for aiming and pointing of the tool. The rear surface 54 extends at an angle to the support surface 76 forwardly and upwardly to guide a user's hand when grasping the handle- forming housing portion 48 and urging the tool forwardly into a workpiece, upwardly into engagement with the support surface 76. The switch 50 is carried at a location on the rear surface 54 relative the support surface 76 that a user's palm overlies switch 50 when the upper surfaces of the user's hand engages the support surface 76. A rearward extension of the axis 40 extends through switch 50. The forwardly and upwardly angled rear surface 54 and the support surface 76 effectively converge in a U-shape as seen in side view. The embodiments disclosed show the support surface 76 extending both rearwardly from the rear surface 54 and sideways from each side surface 53 and 55, as is prefeπed. However, it is within the scope of the invention that the support surface 76 extends only rearwardly from rear surface 54 or only sideways from the side surfaces 53 and 55. If the support surface 76 extends only rearwardly from rear surface 54, the support surface 76 will still engage the upper surface of a user's hand rearward of where the palm engages the rear surface 54. If the support surface 76 extends only sideways from the surfaces 53 and 55 and not rearwardly of rear surface 54, then the support surface 76 will still engage the upper surfaces of the thumb and index finger. In either case, the support surface 76 will still assist in guiding a user's hand into a desired engagement with the tool and assist in supporting the tool while reducing hand and arm fatigue. The screwgun illustrated is for use with an electric motor which is shown to be powered by electricity from a flexible cord 78 to a suitable power source. The tool is shown as having a spring clip 80 on one side as for clipping the tool to a user's belt. The screwgun 10 is provided at the forwardmost end of the second housing portion 46, and as part of the takeoff mechanism 20, with a cylindrical coupling surface 82 coaxially about the hex coupling 22 and, therefore, the takeoff axis 40. Reference is now made to Figure 6 which shows a screwgun 10 as illustrated in Figures 1 to 5 to which a driver attachment 112 is secured. The driver attachment 112 is adapted to receive a collated screwstrip 114 with spaced screws 116 to be advanced by the driver attachment 112, located in alignment with a screwdriver bit and subsequently driven into a workpiece on the user urging the screwgun 10 into a workpiece. The structure of the prefeπed driver attachment 112, shown in Figure 6, is the same as that taught by U.S. Patent 5,568,753 of Habermehl et al, issued October 29, 1996 which is incorporated herein by reference. In overview, the driver attachment 112 has a rearwardly directed socket 127 complementary to the cylindrical surface 82 on the screwgun for coupling of the driver attachment 112 to the screwgun and with a driver shaft (not shown) to be received in the hex coupling 22. The driver attachment has a housing 118 which is secured to the housing 12 of the screw gun via the socket 127. A slide body 120 is slidable relative the housing coaxially about the drive shaft for reciprocal inward and outward movement and is biased by a spring (not shown) outwardly away from the housing 118. The slide body carries a guide mechanism for guiding screws in the screw strip into and maintaining a screw to be driven in axial alignment with the drive shaft and a mechanism for successively advancing screws in the screw strip. The tool shown in Figure 6 comprises a combination in which the screwgun 10 and driver attachment 112 are complementarily chosen having regard to their relative mass and proportion and, preferably, also the mass and proportion of the screw strip 114 such that the geometric center of mass of the combined tool, as seen in side view, will occur between the dashed lines identified as 90 and 91 in Figure 6 and, preferably, proximate the intermediate handle-forming portion 48 and, more preferably, proximate axis 40. Line 90 is intended to represent a line on which the center of mass may reside when the screw strip 114 is full of screws and line 92 when the screw strip is empty of screws. As well, the tool shown in Figure 6 is configured such that if viewed in rear view similar to that of Figure 4, the geometric center of mass would effectively be located in or proximate to the flat plane containing both axis 40 and motor axis 16 about which plane the screwgun 10 is preferably, effectively symmetrical. The driver attachment 112 is secured to support surface 82 oriented such that screw strip 114 extends as a prefeπed straight, relatively rigid strip, vertically downward, centrally through feed channel element 176. As lead screw 117 is aligned with the axis 40, the screw strip extends vertically downward therefrom each screw 116 and, therefore, effectively, the screw strip 114 is symmetrical about the same flat plane containing both axis 40 and motor axis 16. Such weight symmetry of the entire tool including the screw strip about a central plane passing centrally through the handle-forming portion 48 is of assistance in reducing fatigue caused to a user's hand and arm which might otherwise arise if the tool is weighted to one side of this plane as in applying forces necessary to keep the central plane of the tool in a generally vertical position. The weight symmetry with the tool, as shown in Figure 6, and the finite screw strip 114 hanging vertically downwardly is a particularly prefeπed configuration for driving screws horizontally into workpieces such as applying drywall to walls and the present invention includes a method of driving threaded fasteners horizontally into workpieces with tools having such a configuration. Preferably, each of the screw gun 10, driver attachment 112 and screw strip 116 are selected to have configurations such that their mass is symmetrical about a central vertical plane as seen in Figure 6. While the particular weight and configuration of the screwgun 10, its motor 16 and the driver attachment 112 will have a major bearing on the ability to configure a combination tool with a center of gravity at any particular location, as seen in side view in Figure 6, the selection of the screwgun and driver attachment 112 with the screw strip 114 to extend vertically downwardly therefrom, can independently permit substantial location of the center of gravity on a vertical central plane. The tool of Figure 6 illustrates a combination of a screwgun 10 with a removable driver attachment 112. It is to be appreciated that an integral tool dedicated to driving collated screws may be manufactured rather than provide the tool as two principal, separable components. Figure 6 illustrates driver attachment 112 utilizing collated screws on a screw strip of finite length and in which the screw strip is preferably relatively rigid and self-supporting. Such lengths of screw strips could be provided, for example, one or two feet long and can be manually fed into the driver attachment 112 when desired. In the prefeπed configuration shown in Figure 6, the initial length of the strip preferably does not extend a distance measured perpendicular the takeoff axis 40 beyond the lowermost portion of the first housing portion 44. It is to be appreciated that many other driver attachments of different types than those illustrated may be utilized. Known driver attachments for driving collated screw strips include those taught by U.S. Patent 4,146,871 to Mueller et al, issued March 27, 1995 and those taught by the earlier referenced patents refeπed to in the background of the invention of this application. The driver attachments may preferably be used with discrete length collated screw strips or, alternately, with screw strips in a coil and carried in a cartridge or cannister mounted to the driver attachment 112 or to the tool. The driver attachment 112 illustrated in Figure 6 is preferably for use in driving collated screw strips. Collated screw strips are known in which the screws connected to each other by a retaining strip of plastic material. Prefeπed strips are taught, for example, by U.S. Patent 4,167,229, issued September 11, 1979 and its related Canadian Patents 1,040,600 and 1,054,982 as well as U.S. Patent 4,930,630. The invention is not limited to use of the collated screw strips illustrated. Many other forms of screw strips may be used such as those illustrated in U.S. Patents 3,910,324 to Nasiatka; 5,083,483 to Takagi; 4,019,631 to Lejdegard et al and 4,018,254 to DeCaro. Driver attachment adapted to drive other collated screws and/or individual screws and/or other thread fasteners and the like may also be used in accordance with a power tool in accordance with the present invention. Figure 7 shows a power tool generally indicated as drill 310 which is identical to the screwgun 10 of Figures 1 to 4, however, has a modified takeoff mechanism 20 which comprises a conventional chuck 312 as provided on known drills and is adapted to engage and receive drill bits and the like which are to be rotated. It is to be appreciated that the power drill is useful for rotating many known tools such as screwdriver bits, rotary metal files, circular sanding blocks, countersink devices, and the like. It is well known that the chuck 312 includes complementary internally positionable fingers 314 which are adapted to engage cylindrical and/or faceted shafts of bits and the like of varying sizes and to clamp them in place within the chuck for rotation parallel the takeoff axis 40. Reference is made to Figures 8 and 9 which show a second embodiment of a power tool in accordance with the present invention. In Figures 8 and 9, the power tool is shown to be a power drill with its power takeoff mechanism 20 comprising a chuck rotatable about axis 40. The tool has a housing with an enlarged forward housing portion 130 within which a motor (not shown) is disposed. Rearward of the forward housing portion 130, a handle portion 132 is provided which has an exterior shape and size substantially identical to that of the intermediate handle-forming portion 48 in Figures 1 to 7. In this regard, handle portion 132 has upwardly and forwardly sloping rear surface 54 with a slot 52 therein carrying a switch 50 which is activated by forward pressure to operate the drill. The embodiment of Figures 8 and 9 with the motor housed within the housing portion 130 does not have a drive train extend through the handle portion 132. Figure 8 shows in broken lines an optional extension 134 of the handle portion 132 as may be advantageous to carry a battery which is preferably removable. The forward housing portion 130 has a width substantially greater than that of the handle portion 132 as best seen in rear view in Figure 9. As with the embodiments in Figures 1 to 7, the axis 40 extends rearwardly to intersect the palm of a user's hand when the user's hand engages the rear surface 54 of the handle portion 132 and the upper surface 76 of the support mechanism 74 in the preferred manner of use. It is clearly seen that the plate 73 is above axis 40 substantially parallel thereto and extends to the sides and to the rear of the handle portion 132. Reference is now made to Figures 10 and 11 which show a third embodiment of a power tool in accordance with the present invention. Figures 10 and 11 show a power drill having a configuration substantially the same as known drills such as that, for example, shown in U.S. Design Patent 316,021 to Bunyea, issued April 9, 1991, however, with the exception of the addition of the support mechanism 74 and a rear pressure switch 50. In Figures 10 and 11, the power takeoff mechanism 20 comprises a chuck rotatable about axis 40. The tool has a housing with a forward housing portion 130 in which a motor (not shown) is housed and a pistol grip handle 136 extending downwardly at the lower rear of the housing. The pistol grip handle 136 is shown to carry a known trigger switch 140 on its forward surface for depression to operate the drill. A support mechanism 74 comprising a plate 73 with a planar support surface 76 is provided at the upper rear of the housing 130 above a rearward extension of the axis 40. A rear pressure switch 50 is provided on the forwardly and upwardly sloping rear surface 54 of the housing portion 130. In one manner of use, as shown in Figure 10, a user's hand 68 may support the tool with the fingers to extend along one side 53 of the housing under plate 73 and the thumb along the other side 55 of the housing also under the plate 73, with the weight of the tool to be carried substantially by contact with the upper surfaces of the hand as contrasted with grasping pressures applied between the fingers and the thumb. The tool may be operated by applying pressure from the palm of a user's hand forwardly onto the switch 50. Either rear switch 50 or the trigger switch 140 may be used to operate the tool depending upon the manner in which a user's hand may engage the tool. Preferably, the tool of Figures 10 and 11 may have its width, that is, the distance between its sides, selected to be as small as possible at the rear of the housing to assist a user when handling the tool in the prefeπed manner as seen in Figure 10 to be able to comfortably receive the tool resting on the top of his hand between the index finger and his thumb. The sides of the tool may also have a contour which is adapted to assist a user's hand in grasping the tool when the hand is engaged about the tool in a manner as shown in Figure 10. For example, the tool could be provided with recesses in its side proximate the tips of the fingers and the tip of the thumb to assist in grasping the tool when in the position of Figure 10. In every embodiment illustrated, if the support mechanism 74 is disposed to be horizontal, the tool is symmetrical about a vertical plane passing through axis 40 and with each embodiment, the geometric center of mass of the tool preferably lies on this vertical plane. As discussed above, as in the embodiment of Figure 6, it is prefeπed that the geometric center of mass of the tool also be located, when the support member 74 is horizontal, approximately, vertically below where the upper portion of a user's palm engages the rear surface 54 near the support surface 76 as, for example, illustrated by lines 90 and 91 in Figure 6. However, the support mechanism 74 is also particularly useful for power tools in which the tool, including all attachments thereto when used, has a geometric center of mass which is rearward of these lines indicated as 90 and 91 in Figure 6. For example, in the case of the tool shown in Figures 1 and 7, when the tool is grasped by a user's hand as shown in Figure 1 and, assuming that the geometric mass is rearward of the line 90 in Figure 6 as might be expected due to the weight of the motor in the first housing portion 44, then the tool will have an inherent tendency to attempt to pivot clockwise about the intermediate handle portion 48. However, this inherent tendency to rotate is effectively resisted by the upper surface of a user's hand engaging the downwardly directed support surface 76 of the support mechanism 74 without undue tiring of a user's hand or wrist. Moreover, such forces in fact place of some of the weight of the tool ultimately closer to a user's elbow. In contrast, with a tool such as illustrated in Figure 8, with the substantial weight of the tool being in the forward housing portion 130, the tool might be expected to rotate counterclockwise as seen which can, in part, be resisted by engagement between the support surfaces 76 and the thumb and index finger forwardly from the line 140. Nevertheless, the embodiments as shown in Figures 8 and 10 are advantageous insofar as during a driving operation, as with the tools engaged in a workpiece, a user may then urge the tool directly forwardly with his arm maintaining the tool in an operative condition by depression of the rear pressure switch 50 and with the arm comprising a rearward extension of the axis 40. The power tool in accordance with the present invention includes, as preferred embodiments, tools in which the takeoff mechanism provides for rotation about takeoff axis 40. The manner of powering the motor 14 may include many systems including electrical motors powered by AC power from a cord and/or electrical motors powered by batteries. In Figure 1 , the first housing portion 44 for the motor could also provide a storage location for batteries. The invenuon has been illustrated with reference to power tools in which the power takeoff provides a rotary motion about the power takeoff axis 40. The invention is not so limited and the takeoff mechanism could provide for other power takeoff modes such as for vibratory and/or orbital motion sanders and/or belt sanders, reciprocating or rotating saws, crimping devices and metal nibbling devices and scissors and shears and other cutting devices and the like. While the invention has been described with reference to prefeπed embodiments, many modifications and variations of the invention will now occur to those persons skilled in the art. For definition of the invention, reference is made to the appended claims.

Claims: I CLAIM: 1. A power operated hand tool comprising: a front end for urging in a forward direction into a workpiece; a power takeoff at the front end rotatable about an axis; a handle for grasping by a hand of a user; the handle disposed at an acute angle to the axis and having a rearwardly directed rear surface and two opposed side surfaces extending forwardly from the rear surface; a downwardly directed support surface above the handle extending in a forward and rearward direction roughly parallel to the axis; the support surface located above the axis such that a rearward extension of the axis intersects the rear surface below the support surface; the support surface extending sidewardly from each side surface and/or rearwardly from the rear surface for engagement by upper surfaces of an index finger and a thumb of a user's hand when grasping the handle with the palm of the user engaging the rear surface, the fingers extending forwardly from the rear surface on one side surface and the thumb extending forwardly from the rear surface on the other side surface. 2. A tool as claimed in claim 1 wherein the rear surface of the handle extends at an angle to the support surface forwardly and upwardly to guide a user's hand, when grasping the handle and urging the tool forwardly into a workpiece, upwardly into engagement with the support surface. 3. A tool as claimed in claim 1 wherein the support surface is provided as the under surface on a support plate which is disposed above the handle and extends sideways and rearwardly of the handle. 4. A tool as claimed in claim 1 wherein an on/off switch for the tool is carried on the rear surface and is activatable by pressure from the palm of a user's hand being urged forwardly into the rear surface. 5. A tool as claimed in claim 1 including a switch for switching the tool between an inoperative condition and an operative condition; the switch carried on rear surface of the handle and movable between an extended inoperative position in which the switch extends rearwardly from the handle and a retracted operative position in which the switch is retracted forwardly into the handle; the switch biased for movement towards the extended position; wherein on a user's hand engaging the handle, the palm of the user's hand overlies the switch and is urged into the operative retracted position by forward pressure from the palm of a user's hand. 6. A tool as claimed in claim 1 wherein the handle is symmetrical about a flat plane in which the axis lies. 7. A tool as claimed in claim 6 wherein the support surface is substantially normal to said flat plane. 8. A tool as claimed in claim 7 wherein the support surface extends sideways and rearwardly from the rear and side surface of the handle beyond the thickness of a normal index finger of a user. 9. A tool as claimed in claims 1 or 5 including a power drive train extending internally within an elongate housing from a motor disposed near a rear end of the housing through a handle-forming intermediate portion of the housing to the power takeoff in the front end in a front portion of the housing; the intermediate portion forming the handle; the handle-forming portion adapted to be grasped with the fingers and hand of a user to substantially encircle a section of the power drive train passing through the handle-forming intermediate portion. 10. A tool as claimed in claim 9 wherein the motor rotates about a motor axis disposed at an acute angle to the axis of the power takeoff and the handle extends longitudinally about the motor axis, and the motor axis and the axis of the power takeoff lie in a common flat plane. 11. A tool as claimed in claim 1 wherein the support surface extends sideways from each side surface. 12. A tool as claimed in claim 1 wherein the support surface extends rearwardly from the rear surface. 13. A tool as claimed in claim 9 wherein the handle-forming intermediate portion is of reduced circumference compared to portions of the housing about the motor near the rear end. 14. A tool as claimed in claim 10 wherein the housing about the motor is of a circumference greater than a circumference which can be encircled by the fingers and hand of a user. 15. A tool as claimed in claim 10 wherein the motor axis is disposed at an angle of at least 30 to the axis of the power takeoff. 16. A tool as claimed in claim 9 wherein the housing further comprises a first end portion enclosing the motor and a second end portion carrying the power takeoff, the intermediate portion joining the first end portion and the second end portion. 17. A tool as claimed in any one of claims 1 to 16 wherein the tool is a power drill and the power takeoff comprises a chuck rotatable about the second axis. 18. A tool as claimed in any one of claims 1 to 16 wherein the tool comprises a screw gun and the power takeoff comprises a fastener-engaging bit rotatable about the second axis. 19. A tool as claimed in any one of claims 1 to 16 wherein the tool comprises a screwgun for driving screws collated together, spaced from one another in a strip and includes a screwing unit connected to the housing, said screwing unit comprising a guide device for engaging each successive screw to be driven and aligning the same coaxially with the axis of the power takeoff, and a screw feed mechanism for advancing successive screws into the guide device. 20. A tool as claimed in claim 19 wherein a center of mass of the tool is proximate said intermediate handle-forming portion. 21. A tool as claimed in claim 19 wherein said screw strip is substantially straight and extends from the screwing unit with screws substantially symmetrically located about a flat plane including the motor axis and the axis of the power takeoff. 22. A power operated hand tool comprising: a front end for urging in a forward direction into a workpiece; a power takeoff at the front end rotatable about an axis; a handle for grasping by a hand of a user; the handle disposed at an acute angle to the axis and having a rearwardly directed rear surface and two opposed side surfaces extending forwardly from the rear surface; a downwardly directed support surface above the handle extending in a forward and rearward direction roughly parallel to the axis and adapted for engagement by upper surfaces of a user's hand when grasping the handle with a user's palm to engage the rear surface, a user's thumb to extend forwardly therefrom on one side of the handle and a user's fingers to extend forwardly therefrom on the other side of the handle; an on/off switch for the tool is carried on the rear surface and is activatable by pressure from the palm of a user's hand being urged forwardly into the rear surface; the on/off switch carried at a location on the rear surface relative the support surface such that the user's palm overlies the on/off switch when the upper surfaces of the user's hand engage the support surface. 23. A tool as claimed in claim 22 wherein the rear surface of the handle extends at an angle toward the support surface forwardly and upwardly to guide a user's hand when grasping the handle and urging the tool forwardly into a workpiece, upwardly into a position in engagement with the support surface with the palm of the user's hand to overlie the switch. 24. A tool as claimed in claim 22 wherein the support surface and rear surface converge forwardly in a V-shape as seen in side view. 25. A tool as claimed in claim 22 wherein the support surface extends rearwardly from the rear surface and/or sidewardly from the side surface. 26. A tool as claimed in claim 22 wherein a rearward extension of the axis extends through the switch. 27. A tool as claimed in claim 26 wherein a rearward extension of the axis extends through the palm of a user's hand when grasping the handle. 28. A tool as claimed in claim 22 including a power drive train extending internally within an elongate housing from a motor disposed near a rear end of the housing through a handle-forming intermediate portion of the housing to the power takeoff in the front end in a front portion of the housing; the intermediate portion forming the handle; the handle-forming portion adapted to be grasped with the fingers and hand of a user to substantially encircle a section of the power drive train passing through the handle-forming intermediate portion. 29. A hand held power tool with a power drive train extending internally within an elongate housing from a motor disposed near one end of the housing through a handle-forming intermediate portion of the housing to a power takeoff at another end of the housing; wherein the fingers and hand of a user grasp the handle- forming portion to substantially encircle a section of the power drive train passing through the handle-forming portion; the intermediate handle-forming portion has on a rearward side remote from the power takeoff a surface for engagement by the inside surfaces of a palm of a user's hand with the fingers of the user's hand to extend from the palm initially forward approximately parallel the second axis; the second axis, if extended rearwardly, would intersect with the palm of a user's hand when engaged about the handle-forming intermediate portion to grasp the tool. 30. A power operated hand tool comprising: a front end for urging in a forward direction into a workpiece; a power takeoff at the front end rotatable about an axis; a handle for grasping by a hand of a user; the handle disposed at an acute angle to the axis and having a rearwardly directed rear surface and two opposed side surfaces extending forwardly from the rear surface; a downwardly directed support surface above the handle extending in a forward and rearward direction roughly parallel to the axis; the support surface extending sidewardly from each side surface and/or rearwardly from the rear surface for engagement by upper surfaces of an index finger and a thumb of a user's hand when grasping the handle with the palm of the user engaging the rear surface, the fingers extending forwardly from the rear surface on one side surface and the thumb extending forwardly from the rear surface on the other side surface; a power drive train extending internally within an elongate housing from a motor disposed near a rear end of the housing through a handle-forming intermediate portion of the housing to the power takeoff in the front end in a front portion of the housing; the intermediate portion forming the handle; the handle-forming portion adapted to be grasped with the fingers and hand of a user to substantially encircle a section of the power drive train passing through the handle-forming intermediate portion.

Inventors: HABERMEHL G LYLE, HABERMEHL, G., LYLE
Applicants: HABERMEHL G LYLE, HABERMEHL, G., LYLE
Application year: 1996
Main classification: B25F5
IPC codes: B25B21, B25B23, B25F3, B25F5