Cordles power tool system

0001The present invention generally pertains to power tools. More particular, the present invention pertains to a system of cordless power tools. More specifically, but without restriction to the particular embodiment and/or use which is shown and described for purposes of illustration, the present invention relates to a system of cordless power tools with an improved battery pack interface. The present invention also pertains to a related method.

0002Cordless power tools including interchangeable battery units are widely known in the prior art. For example, one such system is shown and described in commonly assigned U.S. Patent No. 3,952,239. United States Patent No. 3,952,239 discloses a system of tools utilizing individual tool heads, each of which incorporates its own essential elements such as a motor and a blade or chuck. This type of system reduces space requirements for tool storage and increases the life span for each motor. Another significant aspect of systems such as that disclosed by U.S. Patent No. 3,952,239 is the fact that they permit improved utilization of incorporated nickel-cadmium batteries and an associated battery charger which are particularly high cost elements of the system.

0003While prior art systems, including but not limited to the type disclosed in U.S. Patent No. 3,952,239, have proven to be suitable for many intended uses, they are all associated with certain disadvantages and/or limitations. A further example of a battery and charger unit of the prior art are disclosed in US 5391972.

0004According to an aspect of the present invention, there is provided a cordless power tool system comprising: <ul id="ul0001" list-style="none" compact="compact"><li>a rechargeable battery pack including a first housing and a battery pack terminal block including a positive terminal blade and a negative terminal blade; and</li><li>a battery charger including a second housing and positive and negative female terminals for receiving the positive and negative terminal blades, respectively, the second housing including a coupling portion for mechanically engaging the battery pack, characterised in that the first housing defines pair of laterally spaced guide rails, that the battery pack terminal block is disposed between the guide rails, that the second housing includes an open deck portion for vertically receiving the battery pack and that the coupling portion defines a pair of laterally spaced grooves for receiving the pair of laterally spaced guide rails such that longitudinal translation of the battery pack toward the coupling portion prevents vertical displacement of the battery pack relative to the second housing.</li></ul>

0005According to another aspect of the present invention, there is provided a method of charging a battery pack for a cordless power tool, the battery pack including a first housing and a battery pack terminal block having positive and negative terminal blades and laterally spaced apart guide rails, the method comprising the steps of: <ul id="ul0002" list-style="none" compact="compact"><li>providing a battery charger having a second housing and positive and negative female terminals recessed within the second housing, the second housing further having a coupling portion;</li><li>mechanically coupling the battery pack and the charger; and</li><li>electrically coupling the positive and negative female terminals with the positive and negative terminal blades, respectively, characterised by providing the battery pack such that the positive and negative terminal blades are disposed between the guide rails, by providing the battery charger with an open deck with which the battery pack is vertically engaged, by providing the battery charger such that the coupling portion comprises a pair of laterally spaced grooves and by the guide rails and the grooves being slidably engaged so as to substantially prevent vertical displacement of the battery pack relative to the charger.</li></ul>

0006Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from a reading of the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings. <ul id="ul0003" list-style="none" compact="compact"><li>Figures 1A-1C are illustrations of a first cordless power tool of a cordless power tool system constructed in accordance with the teachings of a first preferred embodiment of the present invention.</li><li>Figure 2 is an enlarged and exploded perspective view of a first battery pack of the cordless power tool system which is shown in Figure 1A.</li><li>Figure 3 is a top view of the battery pack of Figure 2.</li><li>Figure 4 is a front view of the battery pack of Figure 2.</li><li>Figure 5 is a right side view of the battery pack of Figure 2.</li><li>Figure 6A is an enlarged and exploded perspective view of a tool terminal block carried by the cordless power tool of Figures 1 A-1C.</li><li>Figure 6B is an end view of the main body portion of the tool terminal block.</li><li>Figure 7 is a perspective view of the battery pack terminal block of Figure 2.</li><li>Figure 8 is a cross-sectional view illustrating the interface between the battery pack and tool.</li><li>Figure 9 is a right side view of a second battery pack for the cordless power tool system of the present invention.</li><li>Figure 10 is a right side view of a third battery pack of the cordless power tool system of the present invention.</li><li>Figure 11 is a partially exploded and partially cutaway view illustrating a battery pack charger of the system of the present invention shown operatively associated with the first battery pack.</li><li>Figure 12 is a perspective view of a battery pack charger of Figure 11.</li><li>Figure 13 is a perspective view of a second cordless power tool of the system of the present invention shown operatively associated with a converter.</li><li>Figure 14 is a cross-sectional view illustrating the interface between the cordless power tool and the converter.</li><li>Figure 15 is a side view of a third cordless power tool of the system of the present invention.</li><li>Figure 16 is a schematic representation illustrating the compatibility of the various batteries and tools of the present invention.</li></ul>

0007With general reference to the drawings, a system of cordless power tools constructed in accordance with the teachings of a preferred embodiment of the present invention is illustrated. Exemplary cordless power tools of the system are shown to include, by way of examples, a circular power saw 10 (Figure 1), a reciprocating saw 12 (Figure 13), and a drill 14 (Figure 15). The tools 10-14 each include a conventional DC motor (not shown) adapted to be powered with a common voltage. In the exemplary embodiment, the tools 10-14 are intended to be driven by 24 volt electricity. It will become evident to those skilled that the present invention is not limited to the particular types of tools shown in the drawings nor to specific voltages. In this regard, the teachings of the present invention are applicable to virtually any type of power tool and any supply voltage.

0008With continued reference to the drawings, the system of the present invention is additionally shown to generally include a first rechargeable battery pack 16. The system of the present invention is further shown to generally include an AC/DC converter 18 and a battery charger 20 for charging the battery pack 16. The battery charger 20 is shown in Figure 11 partially cut-away and operatively associated with the battery pack 16. The AC/DC converter is shown in Figure 13 removably attached to the reciprocating saw 12.

0009The focus of the present invention most particularly pertains to the interfaces between the tools 10-14 and the battery pack 16, the interfaces between tools 10-14 and the AC/DC converter 18, and the interfaces between the battery pack 16 and the battery charger 20. During the remainder of this detailed description, it will be understood that the tool interface of each of the tools 10-14 is substantially identical.

0010With particular reference to Figures 2-6, the rechargeable battery pack 16 of the present invention is illustrated to generally include a housing 22, a battery 24 which in the exemplary embodiment illustrated is a 24 volt nickel-cadmium battery, and a battery pack terminal block 26. The housing 22 is shown to include first and second clam shell halves 28 and 30 which are joined at a longitudinally extending parting line 32. Alternatively, it will be understood that the housing 22 may include a pair of halves joined at a laterally extending parting line, or various other constructions including two or more housing portions.

0011The first and second clam shell halves 28 and 30 of the housing 22 cooperate to form an upper portion 34 defining a first chamber 36 and a lower portion 38 defining a second chamber 40. The first chamber 36 receives the battery pack terminal block 26, while the second chamber 40 receives the battery 24. The battery pack terminal block 26 is fixed against lateral and longitudinal movement relative to the housing 22 except for minimal part tolerance stack up. In one application, the battery pack housing 22 has an overall length of approximately 11.5 cm, an overall width of approximately 9.5 cm, and an overall height of approximately 9.5 cm.

0012In the exemplary embodiment, the first and second dam shell halves 28 and 30 of the housing 22 are each unitarily constructed from a rigid plastic or other suitable material. The first and second clam shell haves 28 and 30 are joined by thread-forming fasteners 42. The thread-forming fasteners 42 pass through cooperating apertures 44 and screw boss portions 46 integrally formed with the clam shell halves 28 and 30. Upon assembly, the fasteners 42 form threads in screw boss portions 46 of housing 30. In the exemplary embodiment illustrated, the first clam shell half 28 of the housing 22 is formed to include a peripheral groove 50 adapted to receive a mating rib (not specifically shown) peripherally extending about the second clam shell half 30.

0013To facilitate releasable attachment of the battery pack 16 to the tool 10, the upper portion 34 of the housing 22 is formed to include a pair of guide rails 52. The guide rails 52, which will be described further below, are slidably received into cooperating grooves 54 defined by rails 55 formed in a housing 56 of the tool 10. To further facilitate removable attachment of the battery pack 16 to the tool 10, the upper portion 34 of the housing 22 defines a recess 58. The recess 58 is adapted to receive one or more latch 59 carried by the housing 56 of the tool 10. The latch 59 is conventional in construction and operation and is spring biased to a downward position so as to engage the recess 58 upon insertion with the rechargeable battery pack 16. Removal of the battery pack 16 is thereby prevented until the spring bias of the latch 59 is overcome in a conventional manner insofar as the present invention is concerned.

0014With continued reference to Figures 2-5 and additional reference to Figures 7 and 8, the battery pack terminal block 26 is illustrated to generally include a main body portion 60 constructed of rigid plastic or other suitable material and a plurality of terminals 62. The terminals 62 are generally planar-shaped blade terminals each oriented in a plane substantially perpendicular to a floor 64 (shown in Fig. 2) partially defining the upper chamber 36 of the housing 22. Each blade terminal 62 includes a first end 66 which downwardly extends from the main body portion 60. The blade terminals 62 each further include a second end 68 which forwardly extends. In the preferred embodiment, the second ends 68 of the blade terminals 62 are upwardly spaced from the floor 64. As will be appreciated more fully below, such spacing of the blade terminal 62 from the floor 64 provides improved clearance around the blade terminals 62 and reduces the risk of contamination of the terminals 62 with dirt and other debris. In addition, such spacing of the terminals 62 from the floor 64 allows the contacts of the charger 20 to be more fully enclosed by insulating material. This aspect of the present invention will be discussed more further below. Further in the preferred embodiment, the front tips of the blade terminals 62 and the guide rails 52 are transversely aligned.

0015The main body 60 of the terminal block 26 is shown captured between the clam shell halves 28 and 30 of the housing 22. This arrangement improves assembly by allowing the terminal block 26 to first be electrically attached to the battery 24 and subsequently captured between the clam shell halves 28 and 30. The main body 60 is shown to include a pair of arcuate grooves 70 provided in an under surface thereof for accommodating the screw boss portions 46 of the housing 20 upon assembly. Similarly, an upper side of the main body 60 includes a recess 72 for accommodating the recess 58 of the housing 22. The main body portion 60 is further shown to include a plurality of insulating portions 74 interdisposed between adjacent blade terminal 62 and also positioned outboard of each of the outermost end blade terminals 62. The insulating portions 74 protect the blade terminals 62 from incidental contact or damage.

0016In the exemplary embodiment illustrated, the battery pack terminal block 26 includes four blade terminals 62. Two of the blade terminals 62 are the positive and negative terminals for the battery 24. A third terminal 62 may be used to monitor temperature of the battery 24 and a fourth terminal may be used for battery identification. The particular functions of the third and fourth blade terminals 62 are beyond the scope of the present invention and need not be described in detail herein. It will be appreciated by those skilled in the art that additional terminals 62 may be employed within the scope of the present invention.

0017With particular reference now to Figures 6A-B and 8, a terminal block 76 carried by the tool 10 will be described. The tool terminal block 76 is attached to the housing 56 so as to prevent lateral movement relative to the housing except for part tolerance stack up. In the exemplary embodiment illustrated, the tool terminal block 76 is attached to the housing 56 so as to also prevent longitudinal movement. However, as discussed below, certain applications may desire limited longitudinal translation of the tool terminal block 76.

0018The tool terminal block 76 is illustrated to generally include a main body portion 80, a first or negative terminal member 82, and a second or positive terminal member 84. The first terminal member 82 includes a negative male terminal 86 and a negative female terminal 88. Similarly, the second terminal member includes a positive male terminal 90 and a positive female terminal 92. As will be further discussed below, the female terminals 88 and 92 are adapted to receive the positive and negative blade terminals 62 of the battery pack terminal block 26. The male terminals 86 and 90 are adapted to electrically attach the tool 10 to the converter 18. As shown in Figure 8, when the battery pack 16 is operatively attached to the tool 10, the male terminals 86 and 90 of the tool terminal block 76 are received within clearances, shown in the exemplary embodiment as apertures 96, provided in each of the rails 52. Alternatively, the clearances 96 to accommodate the male terminals 86 and 90 may be in the form of grooves provided in the rails 52 or the rails may be cut back. It will be understood that the male terminals 86 and 90 serve no electrical function when the battery pack 16 is attached to the tool 10.

0019As shown particularly in the end view of Figure 6B and the cross-sectional view of Figure 8, the main body 80 of the tool terminal block 76 includes a plurality of window frames 98 which each define a window or opening 100 for receiving and guiding one of the blade terminals 62. The female terminals 88 and 92 of the tool terminal block 76 are disposed within adjacent ones of the window frames 98. The window frames 98 are generally U-shaped and each include a pair of longitudinally extending legs 102 connected by an intermediate segment 103. Openings 104 are provided between adjacent window frames 98 for receiving the insulating portions 74. In the exemplary embodiment, the ends of each of the legs 102 of the frames 98 are generally triangular in shape so as to define lead-in surfaces for the insulating portions 74 into the openings 104 and also for the terminal blades 62 into their respective opening 100.

0020As shown most clearly in Figure 6B, the main body portion 80 of the tool terminal block 76 includes a pair of laterally spaced rails 97. The main body portion 80 further includes a pair of apertures 101 which receive the male terminals 86 and 90. The rails 97 are adapted to be received within grooves 99 provided in the housing 30 of the battery pack 16 immediately below the guide rails 52. As will be further discussed below, the laterally spaced rails 97 establish a tight fit with the grooves 99 for precisely aligning the tool terminal block 76 with the battery pack terminal block 26.

0021With specific reference to Figure 11, a partially cutaway view of the battery charger 20 of the system of the present invention is shown operatively associated with a battery pack 16 partially removed for purposes of illustration. Figure 12 is an elevated perspective view of the charger 20 shown with the battery pack 16 removed. In the preferred embodiment, the battery charger 20 is a non-isolated charger. As used herein, the term non-isolated will be understood to mean that the output voltage is not isolated from the mains input voltage. The battery charger 20 includes a housing 110 including an open recessed deck 111. The battery charger housing 110 further includes a rear coupling section 112 for mechanically engaging the upper portion 34 of the battery pack housing 22.

0022The rear coupling section 112 includes a pair of opposed grooves 54 similar to that provided in the tool housing 56 which receive the guide rails 52 of the battery pack 22. The battery charger 20 further includes a set of female terminals having at least a pair of female terminals 114 for receiving the positive and negative blade terminals 62 of the battery terminal pack 26. An electrical cord 116 provides AC electricity (for example, 120 volt electricity) to the battery charger 20. Adjacent positioning of the positive and negative terminal blades 62 permits a circuit layout of the charger which reduces electromagnetic interference.

0023The battery charger housing 110 is shown most dearly in Figure 12 to define a plurality of blade terminal openings 140 corresponding in number to the blade terminals 62 of the battery pack 16. The blade terminal openings 140 are defined by insulating portions 142 adapted to cooperatively receive the insulating portions 74 of the battery pack 16. In this regard, adjacent insulating portions 142 are spaced apart to define openings 144 for receiving the insulating portions 74. The insulating portions 142 of the charger housing 110 each include a pair of vertically oriented sidewalls 146 and a horizontally oriented upper segment 148. The upper segments 148 function to conceal the terminals 114 from incidental contact or damage. Since the blade terminals 62 of the battery pack 16 are vertically spaced from the floor 64, the upper segments 148 can be accommodated therebetween. It will be understood by those skilled in the art that the remainder of the battery charger 20 is conventional in construction insofar as the present invention is concerned.

0024The battery pack 16 is loaded into the charger 20 by first vertically positioning the pack 16 on the deck 111 and then sliding the pack 16 rearward to engage the rails 52 of the pack 16 with the grooves 54 of the charger 20. While on the deck 111, the pack 16 is supported by ribs 113. The open deck 111 facilitates location of the pack 16 in the charger 20 since the pack 16 is first grossly aligned with the charger 20 through placement on the deck 111 and then mechanically and electrically connected through a rearward sliding action. A mechanical interface of improved stability is provided. In the event a user lifts the pack 16 and charger 20 by gripping the pack 16 only, the engaged rails 52 and grooves 54 avoid potentially damaging loads on the electrical terminals. Thus, the combination of the loading deck 111 and the rear coupling section 112 provides improved loading ergonomics and mechanical stability of the connection.

0025Tuming now to Figure 13, the converter 18 of the system of the present invention is illustrated operatively attached to the reciprocating saw 12. Again, it will be appreciated by that the particular tool 12 shown in Figure 12 is merely exemplary. In this regard, the converter 18 is operative for use with the circular saw 10 shown in Figure 1, the drill 14 shown in Figure 15, or any other tool similar constructed in accordance with the teachings of the present invention. The converter 18 of Figure 13 is specifically adapted for converting main voltage AC electricity to 24 volt DC electricity.

0026In the preferred embodiment, the converter 18 is a non-isolated converter and includes a housing 120 and an electrical power cord 122. The housing 120 is substantially similar to the housing 22 of the battery pack 16. In this regard, the housing 120 includes first and second clam shell halves joined at a longitudinally extending parting line. Alternatively, the housing 120 may include three (3) or more pieces. An upper portion 122 of the housing 120 includes a pair of guide rails 124 similar to those of the battery pack 16.

0027With continued reference to Figure 13 and additional reference to Figure 14, the converter 18 is shown to include a pair of female terminals 128 adapted to receive the male terminals 86 and 90 of the tool terminal block 76. The female terminals 128 are recessed within the upper portion 122 of the housing 120 of the converter 18. In the preferred embodiment, the female terminals 128 are recessed within the housing 120 of the converter 18 approximately 8mm or more. AC power is converted to DC power by the converter 18 and delivered to the tool 12 through the terminals 128. When the converter 18 is operatively installed on the tool 12, the female terminals 88 and 92 of the tool terminal block 76 are electrically inoperative.

0028As discussed above, the exemplary tools 10-14 shown throughout the drawings are specifically designed to operate on 24 volt DC electricity. With reference to the schematic illustration of Figure 16, the system of the present invention is shown to further include second and third lines B and C of cordless power tools specifically intended for operation at alternate voltages. With the exception of their motors, the second and third lines B and C of power tools are substantially identical to the tools 10-14 of the first line A. For purposes of identification, the tools of the second and third lines B and C are denoted in the drawings with common reference numerals which are primed and double-primed, respectively. It will be understood that the tools 10'-14' and 10"-14"' are powered by second and third voltages, respectively. In the exemplary embodiment, the second and third voltages are lower and higher than the first voltage, respectively. The multiple lines A-C of tools operatively driven by different voltage values provide a consumer with a wide range of selection to accommodate particular power requirements.

0029As shown in Figures 9 and 10, the system of the present invention is illustrated to include second and third battery packs 16' and 16" for providing electricity at the second and third voltages, respectively. The second and third battery packs 16' and 16" are substantially identical in construction to the first battery pack 16. For this reason, reference numerals introduced above with respect to the first battery pack 16 will be used to identify common elements of the second and third battery packs 16' and 16".

0030The third battery pack 16" differs from the first battery pack 16 in that its housing 22 is substantially longer in a longitudinal direction so as to accommodate additional battery cells. In the exemplary embodiment, the width and height dimensions of the third battery pack 16" are identical to corresponding dimensions of the first battery pack 16. The rails 52 of the third battery pack 16" are correspondingly longer as are the grooves 54 formed in the housings 56 of the tools 10□-14□ of the third line.

0031The system of the present invention is intended to prevent operative engagement of any battery pack (e.g., 16 or 16") with a lower voltage value tool so as to protect the electric motors from damage. For example, the higher voltage third battery pack 16" is intended to be locked out of both the tools 10-14 of the first line A and the tools 10'-14' of the second line B. In this regard, the housing 22 of the third battery pack 16" is shown to include a lock-out rib 130. In the embodiment illustrated, the rib 130 extends approximately 86 millimeters from a datum wall 132 and is approximately two millimeters in height and two millimeters in width. The datum wall 132 normally limits translation of the rails 52 relative to the grooves 54. An appropriate stop surface 133 will engage the rib 130 and prevent engagement of the third battery pack 16" which has a higher voltage with the terminal blocks 76 of the tools of the first and second lines A and B.

0032With particular reference to Figure 5, the first battery pack 16 is designed to be locked out of the lower voltage tools 10'-14' of the second line B and will not be long enough to engage the terminal block of the third line C. The first battery pack 16 has a lockout rib 134 which extends approximately 14 millimeters from the datum wall 132. Again, the lockout rib 134 is approximately two millimeters in height and two millimeters in width. While not specifically shown, it will be understood that the grooves 54 of the tools 10-14 of the first line A are formed to accept the lockout rib 134 while the grooves of the tools of the lower voltage second line B are not

0033With specific reference to Figure 9 illustrating the second battery pack 16□, it will be understood that the second battery pack 16' is not specifically intended to be mechanically locked out of any of the tools of any of the lines A-C. However, the length of the battery pack 16', which in the preferred embodiment is identical to that of the first battery pack 16, is insufficient to engage the tool terminal block of the third line C of tools. The battery pack 16' is adapted to work in both the first and second tools lines A and B. In the alternative arrangement discussed above in which the higher voltage third battery pack 16" has a length identical to that of the first and second battery packs 16 and 16', the low voltage second battery pack 16' would not need to be locked out of the tools of the higher voltage tool line C. However, sufficient power may not be available for intended usages. The dashed line between the battery packs 16 and 16' and the tools of the third line C shown in Figure 16 indicates this alternative where electrical engagement is not prevented.

0034Attachment of the battery pack 16 to the housing 56 automatically aligns or centers the blade terminals 62 of the battery pack 16 with the female terminals 88 and 92 of the tool terminal block 76. When the battery pack 16 is inserted into the tool housing 56 the alignment of pack terminal blades 62 and the female tool terminals 88 and 92 occurs in two stages. In a first stage, the guide rails 52 are loosely engaged in the mating tool grooves 54. The total travel of the battery pack 16 relative to the housing 56 is approximately 60 mm. In the second stage, which occurs during approximately the last 22 mm of travel of the pack 16 relative to the housing 56, the grooves 99 in the housing 30 of the battery pack 16 engage the rails 97 of the tool terminal block 76 in a tight fit. In the preferred embodiment, the housing 30 and the alignment rails 97 are in a snug fit. This engagement precisely aligns the battery pack 16 with the tool terminal block 76 and in tum aligns the pack terminal block 26 with the tool terminal block 76. Normally, the blade terminals 62 of the pack 16 will engage the female tool terminals 88 and 92 without further alignment. If the terminal blades 62 are bent, then the terminal blade 62 may engage an associated window frame 98 of the tool terminal block 76. The tapered legs 102 of the frame 98 may aid in straightening a slightly bent terminal blade 62. If the terminal blade 62 is severely bent, entry of the terminal blade 62 into the opening 100 is prevented by the frame 98.

0035As noted above, it may be alternatively desirable to permit the tool terminal block 76 to longitudinally slide in the tool housing 56. When the pack terminal blades 62 are inserted in the female tool terminals 88 and 92 in such an arrangement, the pack terminal blades 62 engage the female tool terminals 88 and 92 and slightly translate the tool terminal block 76 rearwardly. For example, such translation may be on the order of approximately 2mm. When the tool terminal block 76 reaches its limit of travel relative to the tool housing 56, the pack terminals blades 62 are inserted between the female tool terminals 88 and 92. Then, the pack blade terminals 62 are firmly gripped between the female tool terminals 88 and 92. If the battery pack 16 moves relative to the tool housing 56 due to vibration of the tool 10 along an axis parallel to the guide rails 52, the pack 16 and the tool terminal block 76 move together. This conjoint movement of the tool terminal block 76 and the pack 16 may reduce wear on the pack terminal blades 62 and female tool terminals 88 and 92.

0036With particular reference to Figure 2, the battery pack 16 of the present invention is shown to include protrusions 160 to facilitate extraction of the battery pack 16 from the tool housing 56 or from the charger 20. In the exemplary embodiment, each of the housing halves 28 and 30 includes a pair of vertically spaced protrusions 160 disposed on a lateral side of the housing 22 adjacent a rear side of the housing 22. Each protrusion 160 is illustrated to be convexly curved and have a forward portion which the user may directly engage with a thumb or index finger. For example, the width of the battery pack 16 permits the user to engage an upper protrusion 160 of the second housing half 30 with the right thumb and an upper protrusion 160 of the first housing half 28 with the right index finger. The lower protrusions 160 may be used in a substantially similar manner when the battery pack 16 is inverted in the charger 20.

0037The present invention provides a number of advantages. One advantage of the present invention results from providing a battery pack for a cordless power tool with first and second housing halves and defining upper and lower chambers. A battery may be located in the lower chamber and a battery pack terminal block may be located in the upper chamber. Such a construction simplifies assembly, increases the durability of the pack and is particularly suitable for heavy packs having a large number of battery cells.

0038A second advantage of the present invention results from providing a battery pack for a cordless power tool having longitudinally extending guide rails for engaging the tool and longitudinally extending terminal blades located between the rails. The front tips of the terminal blades and the guide rails have transversely aligned front tips. Such a construction simplifies and contributes to the precise alignment of the terminal blades with the guide rails thereby contributing to the alignment of the pack terminal blades with the tool terminals.

0039A third advantage of the present invention results from providing a battery pack for a cordless power tool having a housing defining an upper chamber receiving a terminal block. The terminal block includes a plurality of pack terminals which are perpendicular to and spaced above a floor of the upper chamber thereby providing improved clearance around the terminals and also reducing the potential for contamination of the terminals with debris.

0040A fourth advantage of the present invention results relates to a method of releasably and electrically interconnecting a battery pack with a tool terminal block of a cordless power tool. The battery pack is first roughly centered along a longitudinal axis of the tool handle through engagement of guide rails with the cooperating rails carried by the tool. Then the battery pack is finely centered through engagement of battery pack terminals through engagement of the tool terminal block with the battery pack.

0041A fifth advantage of the present invention is to provide a battery pack for a cordless power tool which includes suitable protrusions to facilitate manual extraction.

0042A sixth advantage of the present invention results from providing a system of cordless power tools including a rechargeable battery pack having male or projecting terminals (for connecting to recessed or female terminals of a tool and to recessed or female terminals of a charger), a non-isolated AC/DC converter having recessed or female terminals for interfacing with the tool, and a non-isolated charger having recessed terminals for interfacing with the battery pack. The use of nonisolated (compared to isolated) components simplify construction and reduce cost. The invention provides a converter with female terminals and a pack with male terminals that are mechanically and electrically compatible with a tool having both male and female terminals. This enables the system to be powered with a cordless DC pack or a corded AC/DC converter and gives the user flexibility in the choice of power sources.

0043A seventh advantage of the present invention results from providing a system of cordless power tools including a charger having a housing with an open recessed deck for vertically receiving a rechargeable battery pack and a coupling portion (preferably, grooves) for mechanically aligning the battery pack and the charger terminals and also connecting the battery pack mechanically in the charger such that longitudinal translation of the battery pack toward the coupling portion prevents vertical displacement of the battery pack relative to the housing. Vertical loading of the pack to an open charger deck initially prior to engaging the pack rails in the mating grooves of the charger simplifies alignment of the pack with the charger grooves. This method is particularly suitable for large heavy battery packs.

0044While the invention has been described in the specification and illustrated in the drawings with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the description of the appended claims.