Saw blade clamping arrangement for a power tool

Abstract: A saw blade clamping arrangement 12 particularly for power reciprocating saws and similar tools 10 having a reciprocating drive shaft 16 connected to a cutting member such as a saw blade 14 includes a clamping member 40 movable relative to the drive shaft 16 between a clamped position and a release position. A threaded fastener 42 passes through an aperture 56 formed in a portion of the clamping member 40 and functions to move the clamping member 40 to its clamped position upon selective rotation. A sleeve 44 surrounds the threaded fastener 56 for rotation therewith. When the sleeve 44 is biased against the clamping member 40 through the force of a biasing member 76, opposing surfaces 72 and 74 prevent rotation of the sleeve 44.

Description: The present invention relates to power tools, and in particular, to a saw blade clamping arrangement for a power tool having a cutting member removably mounted to a reciprocating drive shaft. Power reciprocating saws include jigsaws and other reciprocating saws often referred to in the trade as "recip" saws. These saws incorporate reciprocating drive shafts for driving generally linear saw blades along a rectilinear path to produce a cutting action. US Patent N°. 3496972, representing the closest prior art, describes how a saw blade used with such power tools is attached to the reciprocating drive shaft by a blade holder having a slot for receiving the saw blade and the drive shaft and, a set screw which is received in a hole in the blade holder. Tightening of the set screw operates to clamp the blade against the reciprocating drive shaft. While this manner of saw blade attachment has long proven to be generally satisfactory and commercially successful, it is not without associated disadvantages and is therefore subject to improvement. The primary disadvantage inherently associated with set screw arrangements is attributable to the significant amount of vibrational forces from the cutting action of power reciprocating saws during operation. These vibrational forces frequently result in loosening of the set screw. If the set screw does not remain sufficiently tightened, the saw blade will not remain properly secured to the drive shaft, thereby adversely affecting tool performance and possibly resulting in complete disengagement of the saw blade from the drive shaft. An additional disadvantage with the conventional mounting of saw blades to reciprocating drive shafts relates to an inability quickly and easily to remove saw blades which from time to time become worn or fractured. Because it is often desirable to cut a workpiece with minimum material loss, it is correspondingly desirable to minimise the thickness of the saw blade. As a result, breakage due to the forces encountered during typical use is not an uncommon occurrence. This potential frequency of blade changing makes the ease and rapidity of such action a highly desirable feature for reciprocating saws. A further disadvantage of conventional blade mounting arrangements is the necessity for a separate tool such as a wrench for fixing and removal of the saw blade. These tools are frequently misplaced and time consuming to use. Furthermore, such tools typically require two-handed operation. Various prior attempts have been made to overcome the disadvantages associated with the above-described conventional mounting of saw blades. Many of such prior attempts are directed to the elimination of the use of a set screw. One example of such a saw blade mounting arrangement is shown and described in U.S. Patent No. 5,322,302. The saw blade mounting arrangement taught by U.S. Patent No. 5,322,302 includes a mounting body which functions to urge a clamping sphere through the biasing force of a spring into clamping engagement with a saw blade. Removal of the saw blade is facilitated through actuation of a lever which is selectively operable for overcoming the biasing force exerted by the spring. Operation of this device requires a first of the operator's hands to actuate the lever and a second of the operator's hands for removal or installation of the saw blade. In other words, the actuating lever of this device is not movable to a stable, non-clamping position and necessarily requires two-handed operation, an action which is not always practical or convenient. Other previous attempts to secure saw blades to a reciprocating drive shaft of a power tool without the conventional use of a set screw are shown in U.S. Patent Nos. 3,542,097; 3,823,473; 4,020,555; 4,106,181; 4,441,255; 4,594,781; 4,470,196; 4,528,753; 4,601,477; 4,648,182; 5,103,565; 5,263,972; and 5,324,052. In general, each of the devices taught in these patents represents an attempt to overcome one or more of the disadvantages associated with conventional set screw attachment of a saw blade to a reciprocating drive shaft, including but not limited to the disadvantages discussed above. However, all of these devices are subject to further refinement and improvement. For example, many of the devices, including U.S. Patent No. 5,322,302 discussed above, disadvantageously require two-handed operation. Additionally, by eliminating the set screw, most of the devices disclosed in the above-noted patents are complicated and expensive both to manufacture and assemble as a result of a construction including many separate parts. Furthermore, operation of many of the prior devices requires application of force which is often significant for securing the saw blade in place and loosening of the blade for separation from the drive shaft. Attaining a sufficient force to secure the saw blade to the reciprocating drive shaft often requires the use of a wrench or other tool. Among other disadvantages associated with these prior devices is an inability releasably to attach conventionally shaped saw blades to the reciprocating drive shaft. It is an object of the present invention to provide a saw blade clamping arrangement for a power tool in which the above disadvantages are reduced or substantially obviated. More particularly, it is an object of the present invention to provide a new and improved saw blade mounting arrangement for a power reciprocating saw which retains the known advantages of prior set screw arrangements, including quick and easy operation, and relatively low manufacturing and assembly costs, while eliminating associated disadvantages. The present invention provides a saw blade clamping arrangement for a power tool of the type including a housing, a drive shaft mounted for reciprocating motion relative to the housing, and a saw blade having a haft releasably interconnected with a distal end of the drive shaft for motion along a cutting axis, the saw blade clamping arrangement comprising a clamping body at least partially surrounding the drive shaft and the saw blade, the clamping body being movable relative to the drive shaft between a clamped position for securing the saw blade adjacent to the drive shaft and a release position in which the saw blade may be separated from the drive shaft, a threaded fastener having a head, the threaded fastener engaging an internally threaded aperture which passes through a portion of the clamping body, the threaded fastener including a first and adapted to force one of the saw blade and the drive shaft against the other of the saw blade and the drive shaft when rotated in a first direction and the saw blade clamping arrangement including a sleeve defining a channel and surrounding the threaded fastener, the sleeve cooperating with the head of the threaded fastener for preventing rotation of the threaded fastener relative to the sleeve, a surface of the sleeve cooperating with a side of the clamping body to prevent rotation of the sleeve when the sleeve is in contact with the side of the clamping body; and a biasing member disposed in the channel and operative for providing a biasing force to bias the sleeve against the clamping body. In a preferred embodiment, linear advancement of a threaded fastener operates to move a clamping member between a clamped position and a release position. Further in the preferred embodiment, a sleeve surrounds the threaded fastener which cooperates with the clamping member to prevent loosening of the threaded fastener. The sleeve also provides a mechanical advantage for tightening the threaded fastener. Advantageously, the present invention provides a saw blade clamping arrangement for a power reciprocating saw in which the saw blade can be mounted in place and detached using only a single hand. Additionally, the present invention provides a saw blade mounting arrangement for a power reciprocating saw of simple construction which is relatively inexpensive to manufacture and assemble. Furthermore, the present invention provides a blade mounting arrangement which can accommodate conventional saw blades of various constructions and which can hold the saw blade in place without the need to employ any other tool. A preferred embodiment of a saw blade clamping arrangement according to the present invention, will now be described with reference to the accompanying drawings, in which: Figure 1 is a side elevational view of a reciprocating saw incorporating a saw blade clamping arrangement; Figure 2 is an enlarged, partially cut-away perspective view of the saw blade clamping arrangement of Figure 1; Figure 3 is a side view of the saw blade and drive shaft of Figure 2 shown separated from the saw blade clamping arrangement in order to illustrate the cooperating feature therebetween; Figure 4 is a cross-sectional view taken along the line 4-4 of Figure 2, illustrating the clamping arrangement in its clamped position securely retaining the saw blade adjacent the drive shaft; Figure 5 is a cross-sectional view similar to that of Figure 4, but illustrating the clamping arrangement in its release position in which the blade may be removed from adjacent the drive shaft for replacement; Figure 6 is a further cross-sectional view similar to that of Figure 4, but illustrating the sleeve retracted against the biasing force of the spring and away from the clamping member so as to permit concurrent rotation of the sleeve and the threaded fastener; and Figure 7 is an enlarged side view of the surface of the clamping member adjacent the sleeve illustrating the locking teeth formed thereon which cooperate with substantially identical locating teeth on the sleeve to prevent the threaded fastener from unintentionally backing out. As stated above, the present invention provides an improved saw blade clamping arrangement for a power tool. As illustrated throughout the drawings, the exemplary embodiment of the saw blade clamping arrangement is specifically adapted for a reciprocating power saw. However, the present invention is not so limited in scope or application; and the teachings of the present invention will be understood to be readily adaptable for use with any tool incorporating reciprocating cutting members, including but not limited to reciprocating saws, jig saws, various surgical saws, culinary knives, and related tools whether drawn by power or not. Referring first to Figure 1 of the drawings, in which identical or equivalent elements have been identified with like reference numerals, a power reciprocating saw is identified generally at 10. A saw blade clamping arrangement 12 operatively and releasably attaches a saw blade 14 to a reciprocating drive shaft 16 of the tool 10. In a conventional manner, the power reciprocating saw 10 is powered by a motor (not shown) that is actuated by a trigger switch 18. The delivery of electrical energy to the motor through a power cord (partially shown at 20) is controlled by trigger switch 18. Power tool 10 is shown to include a handle portion 22 which carries trigger switch 18. Power tool 10 is also shown to include a housing 24 that includes a centrally located motor housing portion 26 and a forwardly located gear case housing portion 28. The drive shaft 16 partially extends from a drive shaft channel (not shown) and is operatively connected with a drive mechanism (not shown) housed within gear case housing portion 28. This interconnection between the drive mechanism and drive shaft 16 can be of any known form. The drive shaft 16 is mounted for reciprocating motion generally along the longitudinal axis defined by power tool 10. As shown in Figure 3, the saw blade 14 is of conventional construction. Significantly and as will become apparent below, the saw blade clamping arrangement 12 of the present invention does not depend upon a saw blade 14 having a particular configuration. The saw blade clamping arrangement 12 may readily be adapted releasably to attach any known saw blade to the reciprocating drive shaft. The saw blade 14 shown includes a generally rectangular haft portion 30 and a forwardly extending cutting portion 32 integrally formed therewith and including a plurality of cutting teeth 34. The haft portion 30 includes an aperture 36 for receiving a generally cylindrical locating pin 38 extending from the reciprocating drive shaft 16 and disposed generally perpendicular to the longitudinal axis of the reciprocating drive shaft 16. Referring now generally to Figures 1, 2, and 4 to 6, the saw blade clamping arrangement 12 comprises a clamping member or body 40. The saw blade clamping arrangement 12 further comprises a threaded fastener 42 and a retractable sleeve 44 surrounding the threaded fastener 42. The clamping member 40 is formed to define a generally T-shaped channel 46 adapted to at least partially receive a distal end 48 of the reciprocating drive shaft 16 and the haft portion 30 of the saw blade 14. As shown most clearly in the cross-sectional views of Figures 4 to 6, a first portion 50 of the T-shaped channel 46 receives the haft portion 30 of the saw blade 14 and a second portion 52 of the T-shaped channel 46 which is oriented perpendicular to the first portion 50 receives the distal end 48 of the reciprocating drive shaft 16. The height of the first portion 50 is closely toleranced to the height of the haft portion 30 of the saw blade 14 so that rotation of saw blade 14 about the locating pin 38 is substantially precluded. Similarly, the height of the second portion 52 is closely toleranced to a corresponding dimension of the distal end 48 of the drive shaft 16. The distal end 48 of the drive shaft 16 is movable within the T-shaped channel 46 between a first position (shown in Figure 4) and a second position (shown in Figure 5). In the first position, the clamping member 40 abuts saw blade 14. When the distal end 48 of the drive shaft 16 is moved to the second position, the saw blade 14 can be removed from the T-shaped channel 46 and replaced. The threaded fastener 42 of the saw blade clamping arrangement 12 of the present invention is located partially within, and extends through, an internally threaded aperture 56 formed in a portion of the clamping member 40. The aperture 56 is located in a side 58 of the clamping member 40 which is positioned adjacent the sleeve 44 and extends through the clamping member 40 to the T-shaped channel 46. Selective rotation of the threaded fastener 42 results in corresponding linear movement of the threaded fastener 42 towards or away from the reciprocating drive shaft 16. Specifically, upon clockwise rotation of the threaded fastener 42, a first end 60 of the threaded fastener 42 engages the reciprocating drive shaft 16 and forcibly displaces the reciprocating drive shaft 16 against the saw blade 14. As a result, the locating pin 38 on the reciprocating drive shaft 16 engages the aperture 36 located in the haft portion 30 of the saw blade 14, thereby preventing removal of the saw blade 14 from its operative position adjacent the reciprocating drive shaft 16. The clamping force applied to the saw blade 14 by the reciprocating drive shaft 16 is opposed by an abutting interior surface 62 of the clamping member 40. In the embodiment illustrated, the first end 60 of the threaded fastener 42 is not joined for motion with the drive shaft 16. However, in certain applications, such an arrangement may be desirable. For purposes which will become apparent immediately below, the threaded fastener 42 includes a generally rectangular head 64. The sleeve 44 of the saw blade clamping arrangement 12 of the present invention circumferentially surrounds the rectangular head 64 of threaded fastener 42. As such, the sleeve 44 defines a generally rectangular channel 66 roughly corresponding in size to the head 64 of the threaded fastener thereby to prevent rotation of the head 64 relative to the sleeve 44. The sleeve 44 is formed to include a radially enlarged first end 68 which provides a mechanical advantage for rotating the threaded fastener 42. A surface 70 of the sleeve 44 cooperates with the side 58 of the clamping member 40 to prevent rotation of the sleeve 44 when the sleeve 44 abuts the clamping member 40. In this regard, the side 58 of the clamping member 40 and the surface 70 of the sleeve 44 are formed to include cooperating engagement members. As shown in the cross-sectional view of Figure 7, the cooperating engagement members located on the surface 70 of the sleeve 44 preferably comprise a plurality of radially spaced teeth 72. While not specifically shown, a substantially identical plurality of radially spaced teeth 74 (shown in Figure 2) is formed on the side 58 of the clamping member 40. A biasing member 76 is located within the channel 66 and operates to exert a force for biasing the sleeve 44 into engagement with the clamping member 40. The spring 76 surrounds a portion of the threaded fastener 42 and is located between the head 64 of the threaded fastener 42 and an internal flange 78 of the sleeve 44. Rotation of the threaded fastener 42 relative to the clamping body 40 requires retraction of the sleeve 44 in a direction away from the clamping body 40. Once the surface 70 of the sleeve 44 and the side 58 of the clamping member 40 are spaced apart (as shown in Figure 6), the threaded fastener 42 can be rotated through corresponding rotation of the sleeve 44. With particular reference to Figures 4 to 6, the operation of the clamping arrangement 12 will now be described. Beginning with saw blade 14 securely and operatively interconnected to the reciprocating drive shaft 16 as shown in Figure 4, inadvertent loosening of the threaded fastener 42 from the vibrational forces generated by the tool 10 is opposed by the cooperating pluralities of teeth 72 and 74 formed on the surface 70 of the sleeve 44 and the side 58 of adjacent clamping member 40, respectively. Selective rotation of the sleeve 44 correspondingly rotates the threaded fastener 42, thereby causing the first end 60 of the threaded fastener 42 to be displaced from the reciprocating drive shaft 16. At this point, the reciprocating drive shaft 16 can be translated to its release position within the channel 46 (as shown in Figure 5) and the blade 14 can be removed from the channel 46. Once the saw blade 14 is replaced, rotation of the sleeve 44 in the opposite direction linearly advances the first end 60 of the threaded fastener 42 into engagement with the reciprocating drive shaft 16. As a result, the reciprocating drive shaft 16 is advanced to its clamped position within the channel 46 adjacent the saw blade 14 and a clamping force is created by pressing of the saw blade 14 against the opposing surface 62 of the clamping body 40.

Claims: A saw blade clamping arrangement (12) for a power tool (10) of the type including a housing (24), a drive shaft (16) mounted for reciprocating motion relative to the housing (24), and a saw blade (14) having a haft (30) releasably interconnected with a distal end (48) of the drive shaft (16) for motion along the cutting axis, comprising: a clamping body (40) at least partially surrounding the drive shaft (16) and the saw blade (14), the clamping body (40) being movable relative to the drive shaft (16) between a clamped position for securing the saw blade (14) adjacent to the drive shaft (16) and a release position in which the saw blade (14) may be separated from the drive shaft (16) ; a threaded fastener (42) having a head (64), the threaded fastener (42) engaging an internally threaded aperture (56) which passes through a portion of the clamping body (40) ; the threaded fastener (42) including a first end (60) adapted to force one of the saw blade (14) and the drive shaft (16) against the other of the saw blade (14) and the drive shaft (16) when rotated in a first direction characterised in that the saw blade clamping arrangement (12) includes: a sleeve (44) defining a channel (66) and surrounding the threaded fastener (42), the sleeve (44) cooperating with the head (64) of the threaded fastener (42) for preventing rotation of the threaded fastener (42) relative to the sleeve (44), a surface (70) of the sleeve (44) cooperating with a side (58) of the clamping body (40) to prevent rotation of the sleeve (44) when the sleeve (44) is in contact with the side (58) of the clamping body (40) ; and a biasing member (76) disposed in the channel (66) and operative for providing a biasing force to bias the sleeve (44) against the clamping body (40). A saw blade clamping arrangement (12) as claimed in claim 1 wherein the threaded fastener (42) is operative for selectively establishing a clamping force between the drive shaft (16) and the saw blade (14). A saw blade clamping arrangement (12) a claimed in any one of the previous claims wherein the clamping body (40) defines a central channel (46) for receiving the haft (30) of the saw blade (14) and the distal end (48) of the drive shaft (16), the threaded fastener (42) partially extending into the central channel (46). A saw blade clamping arrangement (12) a claimed in any one of the previous claims wherein the sleeve (44) is retractable against the biasing force and away from the clamping body (40) for permitting concurrent rotation of the threaded fastener (42) and the sleeve (44).

Inventors: FORTNEY JODI, HUANG HAYDEN, KUDO KEVAN, FORTNEY, JODI, HUANG, HAYDEN, KUDO, KEVAN
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1997
Main classification: B23D51
IPC codes: B23D51