Abstract:
Mechanism for controlling the rate of travel of a saw as the saw operates and travels upon a radial arm. A housing contains fluid and an axially movable piston and piston rod. A wheel is operably joined to the piston rod and is connected to the piston rod so that the piston rod moves axially as the wheel rotates. A cable is wound upon the wheel and extends from the wheel and is connected to the saw. As the saw is moved upon the radial arm the cable rotates the wheel, and the wheel forces axial movement of the piston rod and the piston. Movement of the piston forces movement of fluid within the housing. The pressure of the fluid controls the rate of axial movement of the piston and the piston rod and controls the rate of rotary movement of the wheel. Thus, the rate of travel of the cable and the rate of travel of the saw are controlled by the rate at which the piston travels as the piston moves fluid within the housing.

Description:
BACKGROUND OF THE INVENTION 
     A radial arm saw is manually moved as the saw is supported upon an arm which extends radially from a support post. The saw has a rotating cutting blade. The saw is manually moved toward and away from the operator of the saw as the saw is operated. The cutting blade rotates in a direction which tends to move the saw outwardly upon the support arm and toward the operator. Therefore, the saw frequently tends to jump and/or to move unexpectedly quickly toward the operator during a cutting operation. Of course, such movement of the saw presents a dangerous condition for the operator. 
     It is an object of this invention to provide a control mechanism for a radial arm saw whereby the operator has complete control of the rate of movement of the saw during a cutting operation. 
     It is another object of this invention to provide such radial arm control mechanism which can be easily and readily installed on an existing radial arm saw assembly. 
     Another object of this invention is to provide such a radial arm saw control mechanism by which the rate of movement of a radial arm saw can be readily adjusted. 
     Another object of this invention is to provide such radial arm saw control mechanism which is dependable in operation and which is long lived. 
     Another object of this invention is to provide such a radial arm saw control mechanism which is relatively small in physical size, but which is capable of controlling a load of significant magnitude. 
     Other objects and advantages of this invention reside in the construction of parts, the combination thereof, the method of construction and the mode of operation, as will become more apparent from the following description. 
     U.S. Pat. Nos. 2,773,524, 3,090,269, and 4,590,831, describe radial arm saw control mechanisms. However, the means for control are different from that of this invention. 
     SUMMARY OF THE INVENTION 
     This invention comprises control mechanism for a radial arm saw. The control mechanism includes a housing. The housing is mounted adjacent a main support post of the radial arm saw assembly. Within the housing is a movable piston. Also, within the housing is a fluid which is engaged by the piston. The housing has a by-pass conduit which directs fluid from one side of the piston to the opposite side of the piston. When the piston moves in one direction fluid is forced by the piston for flow through the by-pass conduit. 
     The piston is attached to an axially movable shaft or piston rod. The piston rod has an extension portion which extends from the housing. A wheel is rotatably mounted adjacent the extension portion of the piston rod. The wheel has a threaded portion. The extension portion of the piston rod has a threaded portion which is in meshed threaded engagement with the threaded portion of the rotatable wheel. The wheel is encompassed by several convolutions of a cable or the like. The cable extends from the wheel to the saw which is supported by the radial arm of the assembly. When the saw is moved along the radial arm in a direction away from the central support post, the cable is drawn in a direction from the wheel, and the wheel is rotated by the cable. Rotation of the wheel and the threaded portion thereof forces the piston rod to move axially. Axial movement of the piston rod forces the piston to move axially against the pressure of the fluid in the housing. Thus, the movement of the saw is restrained by movement of the piston and by movement of the fluid into the by-pass conduit. The rate of movement of the piston is adjustably controlled by an adjustable valve which controls the volumetric rate of flow of fluid into the by-pass conduit. 
     A resilient member, such as a coil spring or the like, rotates the wheel in the reverse direction when the saw moves upon the radial arm toward the central support post. Also, a resilient member, such as a spring or the like, urges reverse movement of the piston when the saw moves upon the radial arm toward the central support post. 
    
    
     BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective view of a radial arm saw assembly upon which saw control mechanism of this invention is mounted and attached to the saw. 
     FIG. 2 is a side elevational view, drawn on a larger scale than FIG. 1, showing the radial arm saw assembly of FIG. 1 and showing the saw control mechanism of this invention. 
     FIG. 3 is an enlarged view taken substantially on line 3--3 of FIG. 2. 
     FIG. 4 is an enlarged sectional view taken substantially on line 4--4 of FIG. 3. This view shows the restraint member of the control mechanism in a deactuated position. 
     FIG. 5 is an enlarged sectional view, similar to FIG. 4, and drawn on substantially the same scale as FIG. 4, and showing the restraint member in an operating position. 
     FIG. 6 is an enlarged sectional view, taken substantially on line 6--6 of FIG. 2. 
     FIG. 7 is an exploded view of the restraint member of the control mechanism of this invention, drawn on substantially the same scale as FIGS. 4 and 5. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a radial arm saw assembly 10, which is mounted upon a support structure 12. The radial arm saw assembly 10 includes a table 16. Attached to the support structure 12 and extending above the table 16 is a sleeve 20. Within the sleeve 20 is a post 22. The post 22 is axially movable within the sleeve 20. The post 22 has attached thereto at the upper portion thereof an arm 26. The arm 26 is pivotal about the axis of the post 22. The arm 26 is shown as being partially enclosed by a cover 30. 
     Movable along the arm 26 and supported by the arm 26 is a carriage 32. Rotatably supported by the carriage 32 is a saw member 38. The saw member 38 and the carriage 32 comprise a saw unit. Partially enclosing the saw member 38 is a cover 40. A tube 42 extends from the cover 40 for discharging saw dust and chips which are formed by operation of the saw member 38. Attached to the carriage 32 is a handle 44, which is adapted to be grasped by an operator of the saw member 38 for movement of the saw member 38 along the arm 26. 
     The control mechanism of this invention comprises a generally flat lower base member 50 and a generally flat upper base member 51, as best shown in FIG. 7. 
     The base members 50 and 51 are substantially identical and are spaced apart and attached together in substantially parallel relationship by means of spacers 56. Bolts 57 extend through the base members 50 and 51 and through the spacers 56 and have attached thereto nuts 58 which, with the bolts 57, secure together the base members 50 and 51. 
     Each of the base members 50 and 51 has an arcuate portion 60 which partially encompasses the post 22. A U-shape yoke 62 also partially encompasses the post 22 and extends between the base members 50 and 51 and has threaded end portions 62a which extend through an attachment member 64. Attached to the threaded end portions are nuts 65, which secure the U-shape yoke 62 to the attachment member 64 and which secure the yoke 62 to the post 22. Thus, the yoke 62 attaches the base members 50 and 51 to the post 22. The yoke 62 snugly attaches the base members 50 and 51 to the post 22 but permits slidable rotative movement of the base members 50 and 51 upon the post 22. 
     As shown, the lower base member 50 is below the upper base member 51, as the base members 50 and 51 are attached to post 22. Below the base member 50 and attached to the post 22 is an engagement band 66 of flexible plastics material or the like. The band 66 encompasses at least a major portion of the circumference of the post 22. Within the band 66 is a clamping band 68. The clamping band 68 is of metal material or the like, and secures the engagement band 66 in firm engagement with the post 22. 
     The lower base member 50 rests upon the engagement band 66 and the clamping band 68. As the lower base member 50 rests upon the engagement band 66 and the clamping band 68, the yoke 62 and the base members 50 and 51 can pivotally move about the post 22 as the base members 50 and 51 are supported by the post 22. 
     Each of the base members 50 and 51 has an opening 70 therethrough. The openings 70 are in alignment. Mounted upon the base member 51 immediately above the openings 70 is a housing 74. Within the housing 74 is an elongate cavity 76. Within the cavity 76 is a piston 78. The piston 78 has a passage 80 therethrough. Closing the passage 80 is a check valve 81 which permits downward fluid flow through the passage 80, but prevents upward fluid flow through the passage 80. The piston 78 is attached to a piston rod 82, which extends downwardly from the piston 78 and through the openings 70 in the base members 50 and 51. Encompassing the piston rod 82 is an elongate coil spring 84, which engages the piston 78 and which also engages a bottom wall of the housing 74. The coil spring 84 urges the piston 78 upwardly within the cavity 76. 
     Attached to the piston 78 and extending upwardly therefrom is a stem 86. The stem 86 is shown as being rectangular and extends through a rectangular opening 87 in the upper part of the housing 74. Therefore, the stem 86 and the piston 78 are non-rotatable, and the piston rod 82 is non-rotatable, but axially movable. Attached to the upper part of the housing 74 and extending upwardly therefrom is a cover 88 which encloses the upper part of the stem 86. 
     The piston rod 82 has a lower end 89 which is threadedly attached to a threaded shaft 90. Encompassing the piston rod 82 between the base members 50 and 51 is a wheel 92. The wheel 92 is rotatably supported in bearings 93. The wheel 92 has a downwardly extending shaft extension 94 which has internal threads. The internal threads are in threaded meshed engagement with the threaded shaft 90, which is attached to the piston rod 82, as the threaded shaft 90 extends through the shaft extension 94. 
     Below the lower base member 50 is an enclosure 96 which is attached to the lower base member 50. Within the enclosure 96 is a coil spring 97 which has an end 97a which is attached to the enclosure 96. The coil spring 97 also has an opposite end 97b within a slot 98 in the shaft extension 94. The slot 98 is best shown in FIG. 7. Immediately below the enclosure 96 is a band 99 which attaches a cover member 101 to the shaft extension 94. 
     As shown in FIGS. 4 and 5, the housing 74 has an elongate passage or conduit 100, which is adjacent the cavity 76 and which extends along the cavity 76. An orifice 102 provides fluid communication between the passage 100 and the cavity 76 at the lower portion of the cavity 76. A valve 104 is positioned within the orifice 102 and is adjustable within the orifice 102 to control the rate of volumetric fluid flow through the orifice 102. An orifice 108 provides fluid communication between the passage 100 and the cavity 76 at the upper portion of the cavity 76. 
     As best shown in FIG. 4, several convolutions of a cable 110 encompass the wheel 92. The cable 110 has an end portion attached to the wheel 92. The cable 110 extends from the wheel 92, around a part of the post 22, to a sheave 120, as best shown in FIG. 6. The cable 110 extends from the sheave 120 to a connector member 124. The connector member 124 is releasably attached to, and partially encompasses, a portion of the carriage 32. 
     Attached to the upper base member 51 and extending laterally therefrom is a limb 130. An engagement member 138 is attached to the end portion of the limb 130 and engages the arm 26. Thus, the base members 50 and 51 are pivotally moved upon the post 22 as the arm 26 pivotally moves upon the post 22. 
     Operation 
     During a cutting operation an operator grasps the handle 44, shown in FIG. 1, and draws the carriage 32 and the saw member 38 toward the operator. The saw member 38 cuts a board or the like which is positioned upon the table 16. As the carriage 32 and the saw member 38 are moved toward the operator and away from the post 22, successive portions of the cable 110 are drawn by the carriage 32 in a direction from the post 22. The cable 110 thus causes rotative movement of the sheave 120 as successive portions of the cable 110 move in engagement with the sheave 120. The cable 110 thus causes rotative movement of the wheel 92 as successive portions of the cable 110 unwind from the wheel 92 and move from the wheel 92. Thus, as the carriage 32 and the saw member 38 move in a direction from the post 22, the wheel 92 is rotated. 
     As shown and as stated above, the shaft extension 94 is attached to the wheel 92. The shaft extension 94 has internal threads which are in meshed relationship with the threaded shaft 90. Due to the fact that the piston rod 82 is non-rotatable, the threaded shaft 90 is non-rotatable. Therefore, as the wheel 92 rotates, the threaded shaft 90 and the piston rod 82 are moved downwardly. Downward movement of the piston rod 82 moves the piston 78 downwardly. Downward movement of the piston 78 forces downward movement of the fluid within the cavity 76. The fluid flows from the cavity 76 into the orifice 102 and into the passage 100. The rate of volumetric flow of the fluid from the cavity 76 through the orifice 102 is governed by the adjusted position of the valve 104 within the orifice 102. The fluid flows into the passage 100 and upwardly through the passage or conduit 100 and through the orifice 108 and into the cavity 76 above the piston 78. The fluid can flow downwardly through the passage 80 in the piston 78. The check valve 81 within the passage 80 permits downward flow of fluid through the passage 80 and through the piston 78. Thus, fluid flows from a position above the piston 78 to a position below the piston 78. 
     Due to the fact that the volumetric rate of flow of fluid from the cavity 76 into the passage 100 is controlled by the valve 104 within the orifice 102, the rate of rotation of the wheel 92 is controlled by the valve 104. Thus, the rate of travel of the cable 110 from the wheel 92 is controlled by the valve 104. Thus, the rate of movement of the carriage 32 and the saw member 38 in a direction from the post 22 is controlled by the adjusted position of the valve 104 within the orifice 102. The rate of movement of the saw member 38 during cutting action is thus controlled by the adjusted position of the valve 104. 
     When the saw member 38 and the carriage 32 are moved toward the post 22, the coil spring 97 urges rotative movement of the wheel 92 in a direction to draw the cable 110 toward the wheel 92. Thus, the cable 110 winds upon the wheel 92 as the saw 38 and the carriage 32 are moved toward the post 22. Also, as the wheel 92 is rotated in a direction to wind the cable 110 upon the wheel 92, the spring 84 forces the piston 78 upwardly. Thus, the piston rod 82 and the piston 78 are moved upwardly. 
     Thus, it is understood that the radial arm saw control mechanism of this invention provides means by which the rate at which a saw travels on a radial arm can be adjustably and accurately controlled. Thus, danger to the operator is significantly reduced. Furthermore, the cutting operation of the saw may be enhanced. 
     Although the preferred embodiment of the radial arm saw control mechanism of this invention has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof, and the mode of operation, which generally stated consist in a radial arm saw control mechanism within the scope of the appended claims.