CA2241500A1 - Tensioning apparatus - Google Patents
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- CA2241500A1 CA2241500A1 CA002241500A CA2241500A CA2241500A1 CA 2241500 A1 CA2241500 A1 CA 2241500A1 CA 002241500 A CA002241500 A CA 002241500A CA 2241500 A CA2241500 A CA 2241500A CA 2241500 A1 CA2241500 A1 CA 2241500A1
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- tensioning apparatus
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Abstract
A tensioning apparatus for imparting tension to an object secured between at least first and second attachment points includes a first member to which the object is operably connected, and a second member that is connected to one of the first and second attachment points. The first member is slidingly moveable relative to the second member so that the tensioning apparatus may assume a tension releasing position, wherein the object is not in tension, and a tensioning position, wherein the object is placed in tension between the first and second attachment points. The tensioning apparatus also incorporates a rotatable member that is rotatably connected to the first member. A surface of the rotatable member contacts a surface of the second member as the rotatable member rotates and thereby urges the axis of rotation of the rotating member away from the contacted surface of the second member.
Description
TITLE
Tensioning Apparatus TECHNICAL FIELD AND INDUSTRIAL
APPLICABILITY OF THE INVENTION
The present invention relates to apparatus for selectively placing in tension objects secured at two or more points. More particularly, the present invention relates to a tensioning apparatus adapted for connection to an arm of a device such as, for example, a scroll saw or j ig saw, and that will selectively tension a saw blade or other implement connected to the tensioning apparatus. The present invention finds application in any field in which it is desirable to apply a tensioning force to an object that is secured at two or more points. Examples of possible fields of application of the present tensioning apparatus include its use with woodworking scroll saws and j ig saws and with other reciprocating cutting or sawing devices wherein a sawing or cutting blade must be placed in tension for proper operation of the device.
PI-180909.03 BACKGROUND OF THE INVENTION
Proper operation of many devices requires that a particular element of the device be placed in tension. Examples of such devices include many cutting or sawing devices that incorporate an elongated sawing or cutting blade that is mounted at its two ends to the device. A
particular example of such sawing devices are woodworking scroll saws and jig saws, which commonly include a saw blade connected between the free arms of a generally C-shaped or U-shaped member or "yoke" that is reciprocated about a pivot point located at the closed end of the yoke. Means are provided to connect or disconnect the saw blade between the ends of the yoke's two arms. Typically, at least one end and often times both ends of the saw blade are connected to the ends of the yoke's arms by saw blade holders or chucks that exert a clamping force onto the blade ends. The clamping force may be provided by, for example, threaded advancement of a set screw or rotation of a cam. Examples of saw blade chucks that have been incorporated in scroll saws and jig saws include those disclosed in U.S. Patent Nos.
4,681,006, 4,503,742, 2,099,321, and 1,964,651.
If the saw blade of a scroll saw or jig saw is not sufficiently tensioned between the saw's arms, it may bend on encountering the work piece, will not perform satisfactorily, and may break. If the saw blade is over-tensioned between the arms, it also may break during use.
Although it is important to properly tension the saw blade, it is difficult even to impart tension to a saw blade using the known saw blade chucks. For that reason, de~~ices have been developed for selectively placing a saw blade in tension.
An example of a known releasable saw blade tensioning device is disclosed in U.S. Patent No. 2,721,587, issued October 25, 1955. The jigsaw disclosed in that patent includes a pivotable blade holder attached to the end of the upper arm which can be pivoted between blade tightening and blade releasing positions. In the blade tightening position, a lever can be pivoted into position to lock the blade carrier in place, with the blade under tension. The blade holder does not include means to readily adjust the amount of tension that is applied to the blade.
U.S. Patent No. 4,681,006, issued July 21, 1987, discloses a saw blade tensioning device that is mounted on the end of the upper arm of the C-shaped saw blade yoke of a scroll saw. A saw blade support member that includes a central portion is pivotally connected to the upper arm with a first end extending al ong the upper arm and a second end that may be connected to the saw blade. The saw blade support member may be pivoted on the upper arm between a saw tensioning position and a saw blade tension releasing position.
A manually rotatable cam mounted on the saw blade support member's first end may be rotated to engage a screw member mounted on the upper arm and pivot the saw blade support member into the saw blade tensioning position. The screw member may be threadingly adjusted to adjust the tensioning force imparted by the device. The tensioning device of the '006 patent is an integral part of the upper arm and, therefore, the upper arm must be specially configured to accommodate and co-act with the blade holder to provide the proper range of tensions that may be required during operation of the scroll saw.
U.S. Patent No. 5,088,369 discloses a saw blade tensioning device for a scroll saw that is similar in construction to that of the '006 patent. An articulated portion of the device to which the saw blade is connected is coupled to the saw's upper arm and may be pivoted relative to the upper arm. A caroming mechanism is rotatably mounted to the upper arm and may be rotated to contact and pivot the articulated portion and place the saw blade in tension. Thus, similar to the device of the '006 patent, the upper arm of the '369 patent's device must be specially configured to accept and co-act with the articulated portion.
Considering the limitations inherent in the known saw blade tensioning devices and the importance of properly tensioning the saw blade, the need exists for an improved tensioning apparatus for wood working scroll saws, jig saws, and other reciprocating sawing and cutting devices. More generally, a need exists for an improved apparatus for placing in tension an object coupled between two or more attachment points.
SUMMARY OF THE INVENTION
The present invention addresses the forgoing needs, among others, by providing an improved tensioning apparatus for imparting tension to an obj ect that is to be secured between at least first and second attachment points. The present tensioning apparatus includes a first member to which the object that is to be placed in tension is operably connected, and a second member that is connected to one of the first and second attachment points. The first member is slidingly movable relative to the second member so that the tensioning apparatus may assume a tension releasing position, wherein the obj ect is not in tension, and a tensioning position, wherein the obj ect is placed in tension between the first and second attachment points. The present tensioning apparatus further includes a rotatable member that is rotatably mounted on the first member. A surface of the rotatable member contacts a surface of the second member as the rotatable member is caused to rotate about the foregoing axis of rotation and thereby urges the first member to slide relative to the second member. That sliding movement urges the tensioning apparatus toward the tensioning position and thereby places the object in tension.
As used herein, the phrase "operably connected" describes the condition wherein the obj ect that is to be placed in tension either is directly connected to the tensioning apparatus or is connected to the tensioning apparatus by one or more intermediate members connected intermediate the object and the tensioning apparatus.
So as to attach the tensioning apparatus to one of the first or second attachment points, the second member preferably defines a structure that will fixedly mate with the first or second attachment point, as may be the case. The second member more preferably defines a cavity into which the structure including the first or second attachment point is secured. In order to attach the obj ect to be placed in tension to the tensioning apparatus of the present invention, the first member preferably includes an attachment portion for attaching an obj ect clamping member, such as, for example, a chuck, to the tensioning apparatus. The clamping member secures the object to the tensioning apparatus. Alternatively, the tensioning apparatus of the present invention may incorporate a clamping member (such as, for example, a chuck) that is secured to the first member and to which the object is secured.
In a preferred configuration of the present tensioning apparatus, the rotatable member is an elongate pin member that is rotatably connected to the first member so that the pin member may rotate about an axis that is substantially normal to its longitudinal axis. In that preferred configuration, the surface of the rotatable member that contacts or co-acts with a surface of the second member is an end of the pin member. It is also preferred that the present tensioning apparatus is designed so that the amount of tension that is applied to the object when the tensioning apparatus assumes the tensioning position may be adjusted.
Thus, the first member preferably includes a rotatable pivot pin that is rotatable about its longitudinal axis and that includes a threaded bore having an axis that is substantially normal to the pivot pin's longitudinal axis. In such an arrangement, the pin member includes a threaded region and is threadedly disposed in the pivot pin bore so that the pivot pin may be threadedly advanced into and retracted from the bore to thereby adjust the distance separating the longitudinal axis of the pivot pin and the end of the pin member that contacts the aforementioned surface of the second member. Rotation of the pin member within the pivot pin bore in a direction that increases the distance between the end of the pin member and the longitudinal axis of the pivot pin increases the tension that may be imparted by the tensioning apparatus, and vice versa.
As used herein, "pivot pin" refers to an axle or other suitably configured element that may be rotatably mounted on the first member and to which the rotatable member may be attached. The pivot pin thereby provides an axis about which the rotatable member may rotate relative to the first member.
In a more preferred configuration, the second member includes a cap member and a member having a generally U-shaped cross-section that is composed of opposed lateral walls and a wall spanning the lateral walls. The cap member is releasably connected to the lateral walls to define a cavity for connecting the second member to one of the first and second attachment points. The surface of the second member that is contacted by the end of the pin member is a surface of the cap member. The tensioning apparatus also may include a biasing member for biasing the second member toward the pivot pin's rotational axis to thereby urge the surface of the cap member that is contacted by the end of the pin member into contact with the end. The biasing member may be, for example, a leaf spring, which preferably is connected at its first end to the first member and is connected at its second end to the second member.
Alternatively, the leaf spring being may be connected at its second end to the second member, and the first end of the leaf spring contacts the clamping member and biases the clamping member into a desired orientation.
In one particular application, the present tensioning apparatus is a saw blade tensioning apparatus for a scroll saw or jig saw and that will place the saw blade in tension between the arms of the saw's saw blade yoke. The yoke may be, for example, a generally U-shaped or C-shaped yoke as is known in the art. The tensioning apparatus is connected to a first arm of the yoke, an end of the elongate saw blade is connected to the tensioning apparatus, and the saw blade's second end is connected to the yoke's remaining, second arm using a conventional clamping mechanism. The tensioning apparatus includes a yoke retention member for coupling the tensioning apparatus to one of the yoke's arms, and the tensioning apparatus also includes a saw blade clamping member to which an end of the saw blade may be operably connected. The saw blade retention member is slidingly movable relative to the yoke retention member and may move between a tensioning position, in which the saw blade is placed in tension between the first and second arms, and a tension releasing position, in which the saw blade is not in tension between the first and second arms. The saw blade clamping member includes a rotatable member having a surface that contacts a surface of the yoke retention member during rotation of the rotatable member and thereby urges the saw blade clamping member to slide relative to the yoke retention member from the tension releasing position into the tensioning position.
The present invention also is directed to a machine such as, for example, a woodworking scroll saw or jig saw, comprising a table for supporting a work piece thereon, a base supporting the work table, a yoke member having first and second arms and mounted for pivotal motion at a pivot point on the base, and a motor mounted on the base for driving the yoke member to reciprocate about the pivot point. The machine also includes a tensioning apparatus for placing an obj ect such as, for example, a saw blade, in tension between the yoke's first and second arms.
The tensioning apparatus is constructed according to the present invention and as generally described in the immediately preceding paragraph.
The tensioning apparatus of the present invention provides a means to quickly and easily place an object in tension between at least two points. The invention also provides a convenient means to adjust the tension imparted by the apparatus, and the invention may be configured as necessary to adapt it to the particular application in which it is used.
The reader will appreciate the foregoing details and advantages of the present invention, as well as others, upon consideration of the following detailed description of embodiments of the invention. The reader also may comprehend such additional details and advantages of the present invention upon practicing the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention may be better understood by reference to the accompanying drawings in which:
FIG. 1 is perspective view of an embodiment of the tensioning apparatus of the present invention wherein the elements are depicted in a tensioning position;
FIG. 2 is a side elevational view of the embodiment shown in FIG. 1 and wherein the elements are depicted in a tensioning position;
FIG. 3 is a side elevational view of the embodiment shown in FIG. 1 (viewed in the direction of arrows II-II of FIG. 2) and wherein the elements are depicted in a tensioning position;
FIG. 4 is a side elevational view of the embodiment shown in FIG. 1 and in partial cross-section, and wherein the elements are depicted in a tension releasing position;
FIGS. 5 and 6 are side elevational views of the embodiment shown in FIG. 1 and in partial cross-section, and wherein the elements are depicted in positions other than in a tension releasing position or a tensioning position;
FIG. 7 is a side elevational view of the embodiment shown in FIG. 1 and in partial cross-section, and wherein the elements are depicted in a tensioning position;
and FIG. 8 is a side elevational view of a scroll saw having the tensioning apparatus embodiment shown in FIG. 1 connected thereto.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, which are for the purpose of illustrating an embodiment of the invention and not for the purpose limiting the same, an embodiment of a scroll saw saw blade tensioning apparatus 10 constructed in accordance with the present invention is generally illustrated in FIGS. 1-3 and includes first member 16 and second member 18. The first member 16 is slidingly moveable relative to the second member 18 as further described below. Elongated pin member 19 is connected to the first member by pivot pin 21 that may rotate relative to the first member 16 about an axis defined by the longitudinal axis of the pivot pin 21. As pivot pin 21 rotates about its longitudinal axis, the pin member 19 also rotates in the directions indicated by the two-headed arrow in FIG. 1 about an axis that is substantially normal (i. e., perpendicular) to the longitudinal axis of the pin member 19.
As further shown in FIGS. 1-3, the tensioning device 10 also may incorporate a saw blade clamping device 20 that is connected to the lower end 22 of first member 16, for example, by fastener 24. The saw blade clamping device 20 depicted in the accompanying figures is that described in U.S. Patent No. 5,363,733, issued November 15, 1994. It will be understood, however, that the present tensioning device may incorporate any device or arrangement of elements in place of clamping device 20 that will allow the object that is to be placed in tension to be attached to the first member 16. The particular construction of the clamping device will depend upon the particular application of the present tensioning device and, with regard to the embodiment shown in FIGS. 1-3, may be, for example, any of the known scroll saw saw blade clamping devices that are suitably adapted for connection to the lower end 22 of first member 16. Such known scroll saw blade clamping devices include those disclosed in, for example, U.S. Patent Nos. 4,681,006, 2,009,321, 1,964,651, and 1,887,705. The present invention also may be constructed so that it does not include an object clamping device but, instead, is constructed so that such a clamping device may be attached to the first member. Thus, it will be understood that an obj ect clamping device may be, but is not necessarily, an element of the present invention.
Referring again to FIGS. 1-3, the construction of first member 16 will now be described. The lower end 22 of the first member 16 has a cross-section that is substantially of a "U" shape and is defined by two substantially parallel lower walls 26a and 26b connected by wall 28. As best shown in FIG. 1, a connecting portion 30 of clamping device 20 is interposed between lower walls 26a and 26b and fastener 24 is secured through aligned bores in each of the lower walls 26a and 26b and through a bore in the connecting portion 30. The first member 16 also includes an upper portion 34 consisting of two opposed substantially parallel upper walls 32a and 32b that are extensions of regions of the lower walls 26a and 26b. In contrast to the lower portion 22 of the first member 16, the opposed walls 32a and 32b of the upper portion are not connected by a third wall and, therefore, as indicated in FIGS. 3-7, the gap defined between the upper walls 32a and 32b is continuous. Pivot pin 21 is disposed through aligned bores in the upper walls 32a and 32b and is retained therethrough by retainer 36, which secures a portion of the pivot pin 21 and prevents the pivot pin 21 from passing back through the aligned bores.
Although retainer 36 secures the pivot pin 21 through the aligned bores in the upper portion 34; it also allows the pivot pin 21 to rotate about its longitudinal axis within the bores through which it is secured.
Pin member 19 is connected to the first member 16 as follows. As best shown in FIGS. 1 and 3, pivot pin 21 includes a central portion 40 having a threaded bore 42 therethrough. The position of the threaded bore 42 is also indicated in each of FIGS. 4-7, which depict the pivot pin 21 sectioned normal to its longitudinal axis and through threaded bore 42.
Referring to FIG. 4, pin member 19 includes a substantially cylindrical portion 44 having a threaded region 46 and terminating in a rounded end 48. Threaded region 46 is introduced into threaded bore 42 of the pivot pin 21 and may be threadedly advanced or retracted within threaded bore 42 by rotating pivot pin 21 around its longitudinal axis in a suitable clockwise or counterclockwise direction. Thus, it will be understood that the pin member 19 may be rotated about its longitudinal axis and also may be rotated about the longitudinal axis of the pivot pin 21.
':
To facilitate both such rotational movements, an end of pin member 19 opposite end 48 includes knob 50 of a shape suitable for manipulation by an operator.
Second member 18 includes cap member 50 and housing 52, which are joined together to form a cavity for receiving an end of an arm of a scroll saw yoke as follows. Housing 52 comprises opposed lateral walls 53a and 53b connected by bottom wall 53c and which form a structure having a substantially U-shaped cross-section with straight side surfaces and a straight bottom surface. As best shown in FIG. 3, cap member 50 is configured to seat onto lateral walls 53a and 53b opposite to bottom wall 53c and such that the cap member's lateral flanges 54a and 54b flank an upper portion of the lateral walls 53a and 53b. The cap member 50 is secured to the housing 52 by threaded fasteners 56a and 56b which are affixed through a set of spaced-apart smooth bores defined through the cap member 50 and through a set of threaded bores defined through the bottom wall 53c of the housing 52. The sets of bore are aligned and are separated by a distance when the cap member 50 is disposed onto the housing in a proper orientation. It will be understood that when cap member 50 is secured onto housing 52, the elements 50, 53a, 53b, and 53c define a four-sided cavity therebetween, generally indicated as 60 in FIGS. 1 and 3. An interior wall of the cavity, which is defined by the interior surface of lateral wall 53b, is shown in FIGS. 4-7, which are cross-sections taken through cavity 60.
Cavity 60 is dimensioned to receive an end of an arm of the generally C-shaped saw blade yoke of a scroll saw. The end of the arm, for example, may be configured so that the cap member 50 and the housing 52 are disposed about the end of the saw blade yoke and the fasteners 56a and 56b, when fastened through the aligned sets of bore in the cap member 50 and the housing 52, serve both to join those members together and to fixedly secure the tensioning device 10 to the yoke.
Although the accompanying figures depict an embodiment of the present invention that is configured specifically for use with a C-arm scroll saw, it will be understood that, properly configured, the apparatus may be applied in any application in which it is desired to tension an object that is connected at two or more points. Thus, for example, the cavity 60 may be dimensioned as necessary to connect to a particular device to which the object is coupled.
In addition, the second member may lack a cavity 60 and, instead, may include an alternate arrangement of the elements comprising the second member 18 that will allow the tensioning apparatus 10 to be connected to another object.
FIG. 8 depicts the tensioning device 10 secured to a scroll saw. In that figure tensioning device 10 is secured to the upper arm 110 of the saw blade yoke 111 of a scroll saw 112. An upper end of a saw blade 114 is secured to the tensioning device 10 by a saw blade clamp 20, as described above. The remaining, lower end (obscured) of the saw blade may be secured to the lower arm (obscured) of the saw blade yoke 111 by any conventional saw blade clamping device, as described above. The tensioning device 10 may be used in connection with scroll saws of any construction, each of which typically include, as indicated in FIG. 8, a work table 116 for supporting a workpiece (not shown) and a base portion 118 for supporting the work table. The saw blade yoke 111 is driven to reciprocate about a pivot point on the base portion 118, in the vicinity of location 120, by motor 124. The reciprocating motion imparted to the saw blade yoke 111 by motor 124 reciprocates saw blade 114 about the work table 116 to provide the saw's cutting action. The scroll saw 112 also may include stand 126 to allow the scroll saw to be a free-standing device. As further described below, the tensioning device 10 may be actuated to place saw blade 114 in tension between the upper (110) and lower arms of saw blade yoke 111.
The first and second members 16 and 18, respectively, are coupled together as follows. The cap member 50 includes a first flange portion 62 that is reduced in width relative to that portion of the cap member defining cavity 60 and that extends from the cap member 50. The first flange portion 62 has a width dimensioned to fit between and closely abut the opposed, inner surfaces of the upper walls 32a and 32b. The flange portion 62 terminates in an orthogonally disposed second flange portion 64 that has a width greater than the distance between the opposed, inner surfaces of upper walls 32a and 32b. Thus, it will be understood that the first flange portion 62 may be seated and slide between the upper walls 32a and 32b in the directions indicated by the two-headed arrow in FIG. 2, while the second flange portion 64, which is wider than the gap defined by opposed upper walls 32a and 32b, retains the first flange portion 62 within that gap. Thus, the first flange portion 62 may slide between the upper walls 32a and 32b in a region defined between an upper position, at which the first flange portion 62 would contact pivot pin 21, and a lower position, at which the lower end of the second flange portion 64 contacts the upper ends of walls 26a and 26b of the first member 16. The cap member 50 moves along with the attached first flange portion 62. In order to better secure the cap member 50 so that will not wobble relative to the first member 16, cap member 16 includes two opposed fins 65a and 65b. As best shown in FIG. 1, a surface of each of fins 65a and 65b closely abuts a surface of upper walls 32a and 32b, respectively, thereby inhibiting relative lateral movement of those elements.
With the foregoing description of the interrelation and range of motion of the cap member 50 relative to the first member 16 in mind, the motion of the first member 16 of the tensioning device 10 relative to its second member 18 will be understood and is best illustrated by the series of positions shown in FIGS. 4-7. FIG. 4 depicts the first flange member 62 near the perimeter of pivot pin 21, i. e., near the first flange member's aforementioned upper position, which also is an extreme of the range of motion of the first member 16 relative to the second member 18. FIG. 6 depicts the lower end 66 of second flange member 64 in contact with the upper end 68 of wall 26b of the first member 16, which is the aforementioned lower position and which also is the other extreme of the range of motion of the first member 16 relative to the second member 18. FIGS. 5 and 7 depict positions of the first member 16 relative to the second member 18 that are intermediate the two positions shown in FIGS. 4 and 6.
In use, the second member 18 of the tensioning device 10 will be fixedly attached to an arm, typically the upper arm, of a saw blade yoke of a scroll saw as generally shown in FIG. 8, and the first member 16 may move relative to the second member as just described. In that environment, movement of the first member 16 from the position shown in FIG. 4 to the position shown in FIG. 7 causes the first member 16 to move upward and away from the lower arm of the scroll saw's saw blade yoke. Thus, a saw blade that is clamped at one end to clamping device 20 while the tensioning device 10 is in the position shown in FIG. 4, may be placed in tension by forcing the first member 16 to move relative to the second member 18 into the position shown in FIG. 7. Accordingly, the configuration and position of the elements of tensioning device 10 shown in FIG. 4 may be referred to as the tension releasing position, while the configuration and position of elements shown in FIG. 7 may be referred to as the tensioning position.
The mode by which the tensioning device 10 may be placed in one of the tensioning and tension releasing positions will now be described. As discussed above, when the present tensioning device is used in connection with a scroll saw (such as with, for example, the scroll saw 112 depicted in FIG. 8), an end of a saw blade is placed within the jaws of the clamping device 20 and may thereby be secured to the scroll saw yoke's upper arm. The other end of the saw blade is fixedly secured to the saw's lower arm by any known means. Before securing the end of the saw blade to the clamping device 20, the pin member 19 and the pivot pin 21 through which it is threaded are rotated about the axis of the pivot pin 21 to the orientation shown in FIG. 4. In that orientation (which is to the extreme clockwise direction as shown in FIG. 4) the clamping device 10 is in the aforementioned tension releasing position.
To place the saw blade in tension between its first and second points of attachment to the scroll saw, pin member 19 and pivot pin 21 are rotated in the direction of the arrow shown in FIG. 4 and will successively pass through the orientations shown in FIGS. 5 and 6, and if the pin member 19 is sufficiently threadedly advanced into the bore 42 in pivot pin 21 the rounded end 48 of the pin member 19 will contact cap member 50 and will slide along cap member 50 and across a surface of first flange portion 62. The second member 18 (which includes housing 52 and cap member 50) is attached to the scroll saw's upper arm, which is at a substantially fixed position relative to the scroll saw's lower arm.
Therefore, as the pin member 19 rotates in the direction of the arrow in FIG. 4, it will force the first member 16 to move relative to the second member 18, and the movement of the first member 16 will be in the direction of the arrow in FIG. 5, which is away from the lower arm of the scroll saw (see FIG. 8).
The resulting increase in the distance between the saw blade's first attachment point (clamping device 20) and second attachment point (a second blade clamping device on the lower arm) places the blade in tension between the two arms.
Although the present embodiment 10 utilizes a pin member 19, it will be understood that a member of any appropriate configuration may be used in place of pin member 19. Such appropriately configured members that may be used in place of a pin member 19 include those members that are rotatable about an axis of rotation located on the first member 16 and that have an end or surface that, on rotation, will contact the second member 18 and force it away from the axis of rotation. Examples of alternatives to the pin member 19 include rotatable cam members having a lobe-shaped protrusion that will contact the second member 18 on rotation of the cam member about an axis of rotation located on the first member 16.
FIG. 6 depicts the configuration wherein the distance between the second member 18 and the pivot pin 21 is maximized. It therefore represents the configuration of maximum tensioning force as among FIGS. 4-7. Continued rotation of the pin member 19 in the direction of the arrow in FIG. 6 places the end 48 of the pin member 19 within groove 70 defined by intersecting surfaces of the first and second flange portions 62 and 64, respectively, as shown in FIG. 7. The tension on the saw blade will tend to securely seat end 48 within groove 70 until the pin member 19 is rotated in the direction of the arrow in FIG. 7 to thereby release the tension on the saw blade and return the clamping device to the tension releasing position of FIG. 4. Thus, the orientation of FIG. 7 is a stable orientation that will maintain the saw blade in tension, and it is therefore referred to as the aforementioned tensioning position.
Because the distance between end 48 and the rotational axis of pivot pin 21 is maximized in the position of elements shown in FIG. 6 and then is somewhat lesser in the tensioning position shown FIG. 7, it will be understood that the inherent resilience of the saw's yoke and/or the saw blade may be utilized to tension the saw blade and maintain the tensioning apparatus 10 in the tensioning position. In the position of FIG. 6, the maximized distance between the aforementioned end and axis may cause the yoke's arms to draw slightly toward each other in a stressed condition if the arms are of a resilient material.
The slight reduction in the distance between the aforementioned end and axis brought about as the tensioning apparatus moves from the position of FIG. 6 and assumes the position shown in FIG. 7 allows the arms to move apart and toward their original, unstressed positions. The tendency of the arms to assume their original, unstressed configuration maintains the saw blade in tension and inhibits end 48 from moving out of groove 70. If the yoke's arms lack resilience and cannot elastically assume a stressed condition, the resilience of the saw blade itself may provide the tensioning force. Typically, the resilience of both the yoke's arms and the saw blade contribute to the proper operation of the tensioning apparatus.
As further shown by the attached FIGS. 3-7, the tensioning apparatus of the invention also may be configured so as to allow the amount of tension applied by the apparatus to be adjusted. It will be understood that the amount of tension generated by the rotation of pin member 19 is a function of the amount of movement of the first member 16 relative to the second member 18 as the clamping device 10 moves from the tension releasing position (FIG. 4) to the tensioning position (FIG. 7). It will be further understood that the amount of relative movement of members 16 and 18 depends directly on the distance separating the end 48 of the pin member 19 from the axis of rotation of the pivot pin 21. As the distance between the end 48 of the pin member 19 and the axis of rotation of the pivot pin 21 increases, the movement of the first member 16 relative to the second member 18 will be increased, and the amount of tension also will increase as the tensioning apparatus 10 is manipulated into the tensioning position from the tension releasing position. The opposite circumstances occur as the distance between end 48 and the rotational axis of the pivot pin 21 is decreased. The distance between end 48 and the rotational axis of pivot pin 21 may be varied by threadedly advancing or retracting the pin member 19 through the threaded bore 42 in the pivot pin 21. Accordingly, threaded advancement or retraction of the pin member 19 within the threaded bore 42 will adjust the resulting tension supplied by the tensioning apparatus 10.
Tensioning apparatus 10 optionally may include a biasing member, such as the leaf spring 72 shown in FIGS. 3-7. Leaf spring 72 is fixedly attached at a first end to the cap member 50 by spot weld 74 and contacts at its second end a surface of the clamping device 20.
Inasmuch as the clamping device 20 is affixed to the first member 16 , the leaf spring 72 exerts force on the cap member 50 and biases the clamping member 20 away from the cap member S0.
That arrangement has the result of biasing the cap member 50 into contact with the pin member 19. The leaf spring 72 thereby has the effect of absorbing vibrations passed to the tensioning apparatus 10 during operation of the scroll saw. As configured and arranged in the embodiment of the present tensioning apparatus 10 shown in FIGS. 1-7, the leaf spring 72 also has the additional effect of maintaining the clamping device 20 in an orientation convenient for inserting the saw blade therein. In one possible alternate arrangement of the elements, the second end of the biasing member may be fixedly secured to the first member 16, and the force exerted by the biasing member will bias the cap member 50 into contact with the pin member 19.
The tensioning apparatus 10 provides for the selective tensioning of a saw blade or other obj ect in a quick and easy manner, and it also incorporates a means for adj usting the tension imparted by the device. Each of the elements of the tensioning apparatus of the present invention may be constructed of a material appropriate for the particular application. For example, each element may be of aluminum, steel, or an iron-based alloy.
Applications differing from that of the foregoing embodiment may require the use of other materials.
Although the foregoing description of an embodiment of the invention has specific application to a scroll saw, an appropriately configured embodiment of the present invention may be employed in any environment wherein it is desirable to place an object in tension between at least two points. Thus, those of ordinary skill in the art will appreciate that various changes in the configurations, details, materials, and arrangement of the elements that have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art, and all such modifications will remain within the principle and scope of the invention as expressed herein in the appended claims.
Tensioning Apparatus TECHNICAL FIELD AND INDUSTRIAL
APPLICABILITY OF THE INVENTION
The present invention relates to apparatus for selectively placing in tension objects secured at two or more points. More particularly, the present invention relates to a tensioning apparatus adapted for connection to an arm of a device such as, for example, a scroll saw or j ig saw, and that will selectively tension a saw blade or other implement connected to the tensioning apparatus. The present invention finds application in any field in which it is desirable to apply a tensioning force to an object that is secured at two or more points. Examples of possible fields of application of the present tensioning apparatus include its use with woodworking scroll saws and j ig saws and with other reciprocating cutting or sawing devices wherein a sawing or cutting blade must be placed in tension for proper operation of the device.
PI-180909.03 BACKGROUND OF THE INVENTION
Proper operation of many devices requires that a particular element of the device be placed in tension. Examples of such devices include many cutting or sawing devices that incorporate an elongated sawing or cutting blade that is mounted at its two ends to the device. A
particular example of such sawing devices are woodworking scroll saws and jig saws, which commonly include a saw blade connected between the free arms of a generally C-shaped or U-shaped member or "yoke" that is reciprocated about a pivot point located at the closed end of the yoke. Means are provided to connect or disconnect the saw blade between the ends of the yoke's two arms. Typically, at least one end and often times both ends of the saw blade are connected to the ends of the yoke's arms by saw blade holders or chucks that exert a clamping force onto the blade ends. The clamping force may be provided by, for example, threaded advancement of a set screw or rotation of a cam. Examples of saw blade chucks that have been incorporated in scroll saws and jig saws include those disclosed in U.S. Patent Nos.
4,681,006, 4,503,742, 2,099,321, and 1,964,651.
If the saw blade of a scroll saw or jig saw is not sufficiently tensioned between the saw's arms, it may bend on encountering the work piece, will not perform satisfactorily, and may break. If the saw blade is over-tensioned between the arms, it also may break during use.
Although it is important to properly tension the saw blade, it is difficult even to impart tension to a saw blade using the known saw blade chucks. For that reason, de~~ices have been developed for selectively placing a saw blade in tension.
An example of a known releasable saw blade tensioning device is disclosed in U.S. Patent No. 2,721,587, issued October 25, 1955. The jigsaw disclosed in that patent includes a pivotable blade holder attached to the end of the upper arm which can be pivoted between blade tightening and blade releasing positions. In the blade tightening position, a lever can be pivoted into position to lock the blade carrier in place, with the blade under tension. The blade holder does not include means to readily adjust the amount of tension that is applied to the blade.
U.S. Patent No. 4,681,006, issued July 21, 1987, discloses a saw blade tensioning device that is mounted on the end of the upper arm of the C-shaped saw blade yoke of a scroll saw. A saw blade support member that includes a central portion is pivotally connected to the upper arm with a first end extending al ong the upper arm and a second end that may be connected to the saw blade. The saw blade support member may be pivoted on the upper arm between a saw tensioning position and a saw blade tension releasing position.
A manually rotatable cam mounted on the saw blade support member's first end may be rotated to engage a screw member mounted on the upper arm and pivot the saw blade support member into the saw blade tensioning position. The screw member may be threadingly adjusted to adjust the tensioning force imparted by the device. The tensioning device of the '006 patent is an integral part of the upper arm and, therefore, the upper arm must be specially configured to accommodate and co-act with the blade holder to provide the proper range of tensions that may be required during operation of the scroll saw.
U.S. Patent No. 5,088,369 discloses a saw blade tensioning device for a scroll saw that is similar in construction to that of the '006 patent. An articulated portion of the device to which the saw blade is connected is coupled to the saw's upper arm and may be pivoted relative to the upper arm. A caroming mechanism is rotatably mounted to the upper arm and may be rotated to contact and pivot the articulated portion and place the saw blade in tension. Thus, similar to the device of the '006 patent, the upper arm of the '369 patent's device must be specially configured to accept and co-act with the articulated portion.
Considering the limitations inherent in the known saw blade tensioning devices and the importance of properly tensioning the saw blade, the need exists for an improved tensioning apparatus for wood working scroll saws, jig saws, and other reciprocating sawing and cutting devices. More generally, a need exists for an improved apparatus for placing in tension an object coupled between two or more attachment points.
SUMMARY OF THE INVENTION
The present invention addresses the forgoing needs, among others, by providing an improved tensioning apparatus for imparting tension to an obj ect that is to be secured between at least first and second attachment points. The present tensioning apparatus includes a first member to which the object that is to be placed in tension is operably connected, and a second member that is connected to one of the first and second attachment points. The first member is slidingly movable relative to the second member so that the tensioning apparatus may assume a tension releasing position, wherein the obj ect is not in tension, and a tensioning position, wherein the obj ect is placed in tension between the first and second attachment points. The present tensioning apparatus further includes a rotatable member that is rotatably mounted on the first member. A surface of the rotatable member contacts a surface of the second member as the rotatable member is caused to rotate about the foregoing axis of rotation and thereby urges the first member to slide relative to the second member. That sliding movement urges the tensioning apparatus toward the tensioning position and thereby places the object in tension.
As used herein, the phrase "operably connected" describes the condition wherein the obj ect that is to be placed in tension either is directly connected to the tensioning apparatus or is connected to the tensioning apparatus by one or more intermediate members connected intermediate the object and the tensioning apparatus.
So as to attach the tensioning apparatus to one of the first or second attachment points, the second member preferably defines a structure that will fixedly mate with the first or second attachment point, as may be the case. The second member more preferably defines a cavity into which the structure including the first or second attachment point is secured. In order to attach the obj ect to be placed in tension to the tensioning apparatus of the present invention, the first member preferably includes an attachment portion for attaching an obj ect clamping member, such as, for example, a chuck, to the tensioning apparatus. The clamping member secures the object to the tensioning apparatus. Alternatively, the tensioning apparatus of the present invention may incorporate a clamping member (such as, for example, a chuck) that is secured to the first member and to which the object is secured.
In a preferred configuration of the present tensioning apparatus, the rotatable member is an elongate pin member that is rotatably connected to the first member so that the pin member may rotate about an axis that is substantially normal to its longitudinal axis. In that preferred configuration, the surface of the rotatable member that contacts or co-acts with a surface of the second member is an end of the pin member. It is also preferred that the present tensioning apparatus is designed so that the amount of tension that is applied to the object when the tensioning apparatus assumes the tensioning position may be adjusted.
Thus, the first member preferably includes a rotatable pivot pin that is rotatable about its longitudinal axis and that includes a threaded bore having an axis that is substantially normal to the pivot pin's longitudinal axis. In such an arrangement, the pin member includes a threaded region and is threadedly disposed in the pivot pin bore so that the pivot pin may be threadedly advanced into and retracted from the bore to thereby adjust the distance separating the longitudinal axis of the pivot pin and the end of the pin member that contacts the aforementioned surface of the second member. Rotation of the pin member within the pivot pin bore in a direction that increases the distance between the end of the pin member and the longitudinal axis of the pivot pin increases the tension that may be imparted by the tensioning apparatus, and vice versa.
As used herein, "pivot pin" refers to an axle or other suitably configured element that may be rotatably mounted on the first member and to which the rotatable member may be attached. The pivot pin thereby provides an axis about which the rotatable member may rotate relative to the first member.
In a more preferred configuration, the second member includes a cap member and a member having a generally U-shaped cross-section that is composed of opposed lateral walls and a wall spanning the lateral walls. The cap member is releasably connected to the lateral walls to define a cavity for connecting the second member to one of the first and second attachment points. The surface of the second member that is contacted by the end of the pin member is a surface of the cap member. The tensioning apparatus also may include a biasing member for biasing the second member toward the pivot pin's rotational axis to thereby urge the surface of the cap member that is contacted by the end of the pin member into contact with the end. The biasing member may be, for example, a leaf spring, which preferably is connected at its first end to the first member and is connected at its second end to the second member.
Alternatively, the leaf spring being may be connected at its second end to the second member, and the first end of the leaf spring contacts the clamping member and biases the clamping member into a desired orientation.
In one particular application, the present tensioning apparatus is a saw blade tensioning apparatus for a scroll saw or jig saw and that will place the saw blade in tension between the arms of the saw's saw blade yoke. The yoke may be, for example, a generally U-shaped or C-shaped yoke as is known in the art. The tensioning apparatus is connected to a first arm of the yoke, an end of the elongate saw blade is connected to the tensioning apparatus, and the saw blade's second end is connected to the yoke's remaining, second arm using a conventional clamping mechanism. The tensioning apparatus includes a yoke retention member for coupling the tensioning apparatus to one of the yoke's arms, and the tensioning apparatus also includes a saw blade clamping member to which an end of the saw blade may be operably connected. The saw blade retention member is slidingly movable relative to the yoke retention member and may move between a tensioning position, in which the saw blade is placed in tension between the first and second arms, and a tension releasing position, in which the saw blade is not in tension between the first and second arms. The saw blade clamping member includes a rotatable member having a surface that contacts a surface of the yoke retention member during rotation of the rotatable member and thereby urges the saw blade clamping member to slide relative to the yoke retention member from the tension releasing position into the tensioning position.
The present invention also is directed to a machine such as, for example, a woodworking scroll saw or jig saw, comprising a table for supporting a work piece thereon, a base supporting the work table, a yoke member having first and second arms and mounted for pivotal motion at a pivot point on the base, and a motor mounted on the base for driving the yoke member to reciprocate about the pivot point. The machine also includes a tensioning apparatus for placing an obj ect such as, for example, a saw blade, in tension between the yoke's first and second arms.
The tensioning apparatus is constructed according to the present invention and as generally described in the immediately preceding paragraph.
The tensioning apparatus of the present invention provides a means to quickly and easily place an object in tension between at least two points. The invention also provides a convenient means to adjust the tension imparted by the apparatus, and the invention may be configured as necessary to adapt it to the particular application in which it is used.
The reader will appreciate the foregoing details and advantages of the present invention, as well as others, upon consideration of the following detailed description of embodiments of the invention. The reader also may comprehend such additional details and advantages of the present invention upon practicing the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention may be better understood by reference to the accompanying drawings in which:
FIG. 1 is perspective view of an embodiment of the tensioning apparatus of the present invention wherein the elements are depicted in a tensioning position;
FIG. 2 is a side elevational view of the embodiment shown in FIG. 1 and wherein the elements are depicted in a tensioning position;
FIG. 3 is a side elevational view of the embodiment shown in FIG. 1 (viewed in the direction of arrows II-II of FIG. 2) and wherein the elements are depicted in a tensioning position;
FIG. 4 is a side elevational view of the embodiment shown in FIG. 1 and in partial cross-section, and wherein the elements are depicted in a tension releasing position;
FIGS. 5 and 6 are side elevational views of the embodiment shown in FIG. 1 and in partial cross-section, and wherein the elements are depicted in positions other than in a tension releasing position or a tensioning position;
FIG. 7 is a side elevational view of the embodiment shown in FIG. 1 and in partial cross-section, and wherein the elements are depicted in a tensioning position;
and FIG. 8 is a side elevational view of a scroll saw having the tensioning apparatus embodiment shown in FIG. 1 connected thereto.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, which are for the purpose of illustrating an embodiment of the invention and not for the purpose limiting the same, an embodiment of a scroll saw saw blade tensioning apparatus 10 constructed in accordance with the present invention is generally illustrated in FIGS. 1-3 and includes first member 16 and second member 18. The first member 16 is slidingly moveable relative to the second member 18 as further described below. Elongated pin member 19 is connected to the first member by pivot pin 21 that may rotate relative to the first member 16 about an axis defined by the longitudinal axis of the pivot pin 21. As pivot pin 21 rotates about its longitudinal axis, the pin member 19 also rotates in the directions indicated by the two-headed arrow in FIG. 1 about an axis that is substantially normal (i. e., perpendicular) to the longitudinal axis of the pin member 19.
As further shown in FIGS. 1-3, the tensioning device 10 also may incorporate a saw blade clamping device 20 that is connected to the lower end 22 of first member 16, for example, by fastener 24. The saw blade clamping device 20 depicted in the accompanying figures is that described in U.S. Patent No. 5,363,733, issued November 15, 1994. It will be understood, however, that the present tensioning device may incorporate any device or arrangement of elements in place of clamping device 20 that will allow the object that is to be placed in tension to be attached to the first member 16. The particular construction of the clamping device will depend upon the particular application of the present tensioning device and, with regard to the embodiment shown in FIGS. 1-3, may be, for example, any of the known scroll saw saw blade clamping devices that are suitably adapted for connection to the lower end 22 of first member 16. Such known scroll saw blade clamping devices include those disclosed in, for example, U.S. Patent Nos. 4,681,006, 2,009,321, 1,964,651, and 1,887,705. The present invention also may be constructed so that it does not include an object clamping device but, instead, is constructed so that such a clamping device may be attached to the first member. Thus, it will be understood that an obj ect clamping device may be, but is not necessarily, an element of the present invention.
Referring again to FIGS. 1-3, the construction of first member 16 will now be described. The lower end 22 of the first member 16 has a cross-section that is substantially of a "U" shape and is defined by two substantially parallel lower walls 26a and 26b connected by wall 28. As best shown in FIG. 1, a connecting portion 30 of clamping device 20 is interposed between lower walls 26a and 26b and fastener 24 is secured through aligned bores in each of the lower walls 26a and 26b and through a bore in the connecting portion 30. The first member 16 also includes an upper portion 34 consisting of two opposed substantially parallel upper walls 32a and 32b that are extensions of regions of the lower walls 26a and 26b. In contrast to the lower portion 22 of the first member 16, the opposed walls 32a and 32b of the upper portion are not connected by a third wall and, therefore, as indicated in FIGS. 3-7, the gap defined between the upper walls 32a and 32b is continuous. Pivot pin 21 is disposed through aligned bores in the upper walls 32a and 32b and is retained therethrough by retainer 36, which secures a portion of the pivot pin 21 and prevents the pivot pin 21 from passing back through the aligned bores.
Although retainer 36 secures the pivot pin 21 through the aligned bores in the upper portion 34; it also allows the pivot pin 21 to rotate about its longitudinal axis within the bores through which it is secured.
Pin member 19 is connected to the first member 16 as follows. As best shown in FIGS. 1 and 3, pivot pin 21 includes a central portion 40 having a threaded bore 42 therethrough. The position of the threaded bore 42 is also indicated in each of FIGS. 4-7, which depict the pivot pin 21 sectioned normal to its longitudinal axis and through threaded bore 42.
Referring to FIG. 4, pin member 19 includes a substantially cylindrical portion 44 having a threaded region 46 and terminating in a rounded end 48. Threaded region 46 is introduced into threaded bore 42 of the pivot pin 21 and may be threadedly advanced or retracted within threaded bore 42 by rotating pivot pin 21 around its longitudinal axis in a suitable clockwise or counterclockwise direction. Thus, it will be understood that the pin member 19 may be rotated about its longitudinal axis and also may be rotated about the longitudinal axis of the pivot pin 21.
':
To facilitate both such rotational movements, an end of pin member 19 opposite end 48 includes knob 50 of a shape suitable for manipulation by an operator.
Second member 18 includes cap member 50 and housing 52, which are joined together to form a cavity for receiving an end of an arm of a scroll saw yoke as follows. Housing 52 comprises opposed lateral walls 53a and 53b connected by bottom wall 53c and which form a structure having a substantially U-shaped cross-section with straight side surfaces and a straight bottom surface. As best shown in FIG. 3, cap member 50 is configured to seat onto lateral walls 53a and 53b opposite to bottom wall 53c and such that the cap member's lateral flanges 54a and 54b flank an upper portion of the lateral walls 53a and 53b. The cap member 50 is secured to the housing 52 by threaded fasteners 56a and 56b which are affixed through a set of spaced-apart smooth bores defined through the cap member 50 and through a set of threaded bores defined through the bottom wall 53c of the housing 52. The sets of bore are aligned and are separated by a distance when the cap member 50 is disposed onto the housing in a proper orientation. It will be understood that when cap member 50 is secured onto housing 52, the elements 50, 53a, 53b, and 53c define a four-sided cavity therebetween, generally indicated as 60 in FIGS. 1 and 3. An interior wall of the cavity, which is defined by the interior surface of lateral wall 53b, is shown in FIGS. 4-7, which are cross-sections taken through cavity 60.
Cavity 60 is dimensioned to receive an end of an arm of the generally C-shaped saw blade yoke of a scroll saw. The end of the arm, for example, may be configured so that the cap member 50 and the housing 52 are disposed about the end of the saw blade yoke and the fasteners 56a and 56b, when fastened through the aligned sets of bore in the cap member 50 and the housing 52, serve both to join those members together and to fixedly secure the tensioning device 10 to the yoke.
Although the accompanying figures depict an embodiment of the present invention that is configured specifically for use with a C-arm scroll saw, it will be understood that, properly configured, the apparatus may be applied in any application in which it is desired to tension an object that is connected at two or more points. Thus, for example, the cavity 60 may be dimensioned as necessary to connect to a particular device to which the object is coupled.
In addition, the second member may lack a cavity 60 and, instead, may include an alternate arrangement of the elements comprising the second member 18 that will allow the tensioning apparatus 10 to be connected to another object.
FIG. 8 depicts the tensioning device 10 secured to a scroll saw. In that figure tensioning device 10 is secured to the upper arm 110 of the saw blade yoke 111 of a scroll saw 112. An upper end of a saw blade 114 is secured to the tensioning device 10 by a saw blade clamp 20, as described above. The remaining, lower end (obscured) of the saw blade may be secured to the lower arm (obscured) of the saw blade yoke 111 by any conventional saw blade clamping device, as described above. The tensioning device 10 may be used in connection with scroll saws of any construction, each of which typically include, as indicated in FIG. 8, a work table 116 for supporting a workpiece (not shown) and a base portion 118 for supporting the work table. The saw blade yoke 111 is driven to reciprocate about a pivot point on the base portion 118, in the vicinity of location 120, by motor 124. The reciprocating motion imparted to the saw blade yoke 111 by motor 124 reciprocates saw blade 114 about the work table 116 to provide the saw's cutting action. The scroll saw 112 also may include stand 126 to allow the scroll saw to be a free-standing device. As further described below, the tensioning device 10 may be actuated to place saw blade 114 in tension between the upper (110) and lower arms of saw blade yoke 111.
The first and second members 16 and 18, respectively, are coupled together as follows. The cap member 50 includes a first flange portion 62 that is reduced in width relative to that portion of the cap member defining cavity 60 and that extends from the cap member 50. The first flange portion 62 has a width dimensioned to fit between and closely abut the opposed, inner surfaces of the upper walls 32a and 32b. The flange portion 62 terminates in an orthogonally disposed second flange portion 64 that has a width greater than the distance between the opposed, inner surfaces of upper walls 32a and 32b. Thus, it will be understood that the first flange portion 62 may be seated and slide between the upper walls 32a and 32b in the directions indicated by the two-headed arrow in FIG. 2, while the second flange portion 64, which is wider than the gap defined by opposed upper walls 32a and 32b, retains the first flange portion 62 within that gap. Thus, the first flange portion 62 may slide between the upper walls 32a and 32b in a region defined between an upper position, at which the first flange portion 62 would contact pivot pin 21, and a lower position, at which the lower end of the second flange portion 64 contacts the upper ends of walls 26a and 26b of the first member 16. The cap member 50 moves along with the attached first flange portion 62. In order to better secure the cap member 50 so that will not wobble relative to the first member 16, cap member 16 includes two opposed fins 65a and 65b. As best shown in FIG. 1, a surface of each of fins 65a and 65b closely abuts a surface of upper walls 32a and 32b, respectively, thereby inhibiting relative lateral movement of those elements.
With the foregoing description of the interrelation and range of motion of the cap member 50 relative to the first member 16 in mind, the motion of the first member 16 of the tensioning device 10 relative to its second member 18 will be understood and is best illustrated by the series of positions shown in FIGS. 4-7. FIG. 4 depicts the first flange member 62 near the perimeter of pivot pin 21, i. e., near the first flange member's aforementioned upper position, which also is an extreme of the range of motion of the first member 16 relative to the second member 18. FIG. 6 depicts the lower end 66 of second flange member 64 in contact with the upper end 68 of wall 26b of the first member 16, which is the aforementioned lower position and which also is the other extreme of the range of motion of the first member 16 relative to the second member 18. FIGS. 5 and 7 depict positions of the first member 16 relative to the second member 18 that are intermediate the two positions shown in FIGS. 4 and 6.
In use, the second member 18 of the tensioning device 10 will be fixedly attached to an arm, typically the upper arm, of a saw blade yoke of a scroll saw as generally shown in FIG. 8, and the first member 16 may move relative to the second member as just described. In that environment, movement of the first member 16 from the position shown in FIG. 4 to the position shown in FIG. 7 causes the first member 16 to move upward and away from the lower arm of the scroll saw's saw blade yoke. Thus, a saw blade that is clamped at one end to clamping device 20 while the tensioning device 10 is in the position shown in FIG. 4, may be placed in tension by forcing the first member 16 to move relative to the second member 18 into the position shown in FIG. 7. Accordingly, the configuration and position of the elements of tensioning device 10 shown in FIG. 4 may be referred to as the tension releasing position, while the configuration and position of elements shown in FIG. 7 may be referred to as the tensioning position.
The mode by which the tensioning device 10 may be placed in one of the tensioning and tension releasing positions will now be described. As discussed above, when the present tensioning device is used in connection with a scroll saw (such as with, for example, the scroll saw 112 depicted in FIG. 8), an end of a saw blade is placed within the jaws of the clamping device 20 and may thereby be secured to the scroll saw yoke's upper arm. The other end of the saw blade is fixedly secured to the saw's lower arm by any known means. Before securing the end of the saw blade to the clamping device 20, the pin member 19 and the pivot pin 21 through which it is threaded are rotated about the axis of the pivot pin 21 to the orientation shown in FIG. 4. In that orientation (which is to the extreme clockwise direction as shown in FIG. 4) the clamping device 10 is in the aforementioned tension releasing position.
To place the saw blade in tension between its first and second points of attachment to the scroll saw, pin member 19 and pivot pin 21 are rotated in the direction of the arrow shown in FIG. 4 and will successively pass through the orientations shown in FIGS. 5 and 6, and if the pin member 19 is sufficiently threadedly advanced into the bore 42 in pivot pin 21 the rounded end 48 of the pin member 19 will contact cap member 50 and will slide along cap member 50 and across a surface of first flange portion 62. The second member 18 (which includes housing 52 and cap member 50) is attached to the scroll saw's upper arm, which is at a substantially fixed position relative to the scroll saw's lower arm.
Therefore, as the pin member 19 rotates in the direction of the arrow in FIG. 4, it will force the first member 16 to move relative to the second member 18, and the movement of the first member 16 will be in the direction of the arrow in FIG. 5, which is away from the lower arm of the scroll saw (see FIG. 8).
The resulting increase in the distance between the saw blade's first attachment point (clamping device 20) and second attachment point (a second blade clamping device on the lower arm) places the blade in tension between the two arms.
Although the present embodiment 10 utilizes a pin member 19, it will be understood that a member of any appropriate configuration may be used in place of pin member 19. Such appropriately configured members that may be used in place of a pin member 19 include those members that are rotatable about an axis of rotation located on the first member 16 and that have an end or surface that, on rotation, will contact the second member 18 and force it away from the axis of rotation. Examples of alternatives to the pin member 19 include rotatable cam members having a lobe-shaped protrusion that will contact the second member 18 on rotation of the cam member about an axis of rotation located on the first member 16.
FIG. 6 depicts the configuration wherein the distance between the second member 18 and the pivot pin 21 is maximized. It therefore represents the configuration of maximum tensioning force as among FIGS. 4-7. Continued rotation of the pin member 19 in the direction of the arrow in FIG. 6 places the end 48 of the pin member 19 within groove 70 defined by intersecting surfaces of the first and second flange portions 62 and 64, respectively, as shown in FIG. 7. The tension on the saw blade will tend to securely seat end 48 within groove 70 until the pin member 19 is rotated in the direction of the arrow in FIG. 7 to thereby release the tension on the saw blade and return the clamping device to the tension releasing position of FIG. 4. Thus, the orientation of FIG. 7 is a stable orientation that will maintain the saw blade in tension, and it is therefore referred to as the aforementioned tensioning position.
Because the distance between end 48 and the rotational axis of pivot pin 21 is maximized in the position of elements shown in FIG. 6 and then is somewhat lesser in the tensioning position shown FIG. 7, it will be understood that the inherent resilience of the saw's yoke and/or the saw blade may be utilized to tension the saw blade and maintain the tensioning apparatus 10 in the tensioning position. In the position of FIG. 6, the maximized distance between the aforementioned end and axis may cause the yoke's arms to draw slightly toward each other in a stressed condition if the arms are of a resilient material.
The slight reduction in the distance between the aforementioned end and axis brought about as the tensioning apparatus moves from the position of FIG. 6 and assumes the position shown in FIG. 7 allows the arms to move apart and toward their original, unstressed positions. The tendency of the arms to assume their original, unstressed configuration maintains the saw blade in tension and inhibits end 48 from moving out of groove 70. If the yoke's arms lack resilience and cannot elastically assume a stressed condition, the resilience of the saw blade itself may provide the tensioning force. Typically, the resilience of both the yoke's arms and the saw blade contribute to the proper operation of the tensioning apparatus.
As further shown by the attached FIGS. 3-7, the tensioning apparatus of the invention also may be configured so as to allow the amount of tension applied by the apparatus to be adjusted. It will be understood that the amount of tension generated by the rotation of pin member 19 is a function of the amount of movement of the first member 16 relative to the second member 18 as the clamping device 10 moves from the tension releasing position (FIG. 4) to the tensioning position (FIG. 7). It will be further understood that the amount of relative movement of members 16 and 18 depends directly on the distance separating the end 48 of the pin member 19 from the axis of rotation of the pivot pin 21. As the distance between the end 48 of the pin member 19 and the axis of rotation of the pivot pin 21 increases, the movement of the first member 16 relative to the second member 18 will be increased, and the amount of tension also will increase as the tensioning apparatus 10 is manipulated into the tensioning position from the tension releasing position. The opposite circumstances occur as the distance between end 48 and the rotational axis of the pivot pin 21 is decreased. The distance between end 48 and the rotational axis of pivot pin 21 may be varied by threadedly advancing or retracting the pin member 19 through the threaded bore 42 in the pivot pin 21. Accordingly, threaded advancement or retraction of the pin member 19 within the threaded bore 42 will adjust the resulting tension supplied by the tensioning apparatus 10.
Tensioning apparatus 10 optionally may include a biasing member, such as the leaf spring 72 shown in FIGS. 3-7. Leaf spring 72 is fixedly attached at a first end to the cap member 50 by spot weld 74 and contacts at its second end a surface of the clamping device 20.
Inasmuch as the clamping device 20 is affixed to the first member 16 , the leaf spring 72 exerts force on the cap member 50 and biases the clamping member 20 away from the cap member S0.
That arrangement has the result of biasing the cap member 50 into contact with the pin member 19. The leaf spring 72 thereby has the effect of absorbing vibrations passed to the tensioning apparatus 10 during operation of the scroll saw. As configured and arranged in the embodiment of the present tensioning apparatus 10 shown in FIGS. 1-7, the leaf spring 72 also has the additional effect of maintaining the clamping device 20 in an orientation convenient for inserting the saw blade therein. In one possible alternate arrangement of the elements, the second end of the biasing member may be fixedly secured to the first member 16, and the force exerted by the biasing member will bias the cap member 50 into contact with the pin member 19.
The tensioning apparatus 10 provides for the selective tensioning of a saw blade or other obj ect in a quick and easy manner, and it also incorporates a means for adj usting the tension imparted by the device. Each of the elements of the tensioning apparatus of the present invention may be constructed of a material appropriate for the particular application. For example, each element may be of aluminum, steel, or an iron-based alloy.
Applications differing from that of the foregoing embodiment may require the use of other materials.
Although the foregoing description of an embodiment of the invention has specific application to a scroll saw, an appropriately configured embodiment of the present invention may be employed in any environment wherein it is desirable to place an object in tension between at least two points. Thus, those of ordinary skill in the art will appreciate that various changes in the configurations, details, materials, and arrangement of the elements that have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art, and all such modifications will remain within the principle and scope of the invention as expressed herein in the appended claims.
Claims (23)
1. A tensioning apparatus for imparting tension to an object secured between at least first and second attachment points, the tensioning apparatus comprising a first member to which the object is operably connected, and a second member that is connected to one of the first and second attachment points, said first member being slidingly moveable relative to said second member so that the tensioning apparatus may assume a tension releasing position, wherein the object is not in tension, and a tensioning position, wherein the object is placed in tension between the first and second attachment points, the tensioning apparatus further comprising a rotatable member that is rotatably connected to said first member, a surface of said rotatable member contacting a surface of said second member on rotation of said rotatable member about said axis of rotation to thereby move said axis of rotation away from said surface of said second member and to thereby urge the tensioning apparatus to assume said tensioning position.
2. The tensioning apparatus recited in claim 1, wherein said rotatable member is an elongate pin member that is rotatably connected to said first member and that may rotate about a rotational axis that is substantially normal to the longitudinal axis of said pin member, and wherein said surface of said rotatable member that contacts said surface of said second member is an end of said pin member.
3. The tensioning apparatus recited in claim 2, wherein said second member defines a cavity for attaching the tensioning apparatus to one of the first and second attachment points.
4. The tensioning apparatus recited in claim 2, wherein said first member comprises an attachment portion for attaching a clamping member to the tensioning apparatus, said clamping member for securing the object thereto.
5. The tensioning apparatus recited in claim 2, wherein said first member comprises a clamping member for securing a portion of the object thereto, said clamping member for connecting the object to the tensioning apparatus.
6. The tensioning apparatus recited in claim 1, wherein an amount of tension that is applied to the object when the tensioning apparatus assumes said tensioning position may be adjusted.
7. The tensioning apparatus recited in claim 2, wherein the first member further comprises a rotatable pivot pin that is rotatable about its longitudinal axis and that includes a threaded bore therethrough having an axis that is substantially normal to said longitudinal axis of said pivot pin, said pin member comprising a threaded region, said pin member threadedly disposed within said bore of said pivot pin so that said pin member may threadedly advance and retract relative to said pivot pin to thereby adjust the distance separating said end of said pin member and said pivot pin.
8. The tensioning apparatus of claim 2, wherein said second member comprises a cap member and also comprises a member having a generally U-shaped cross-section and comprising opposed lateral walls and a wall spanning said lateral walls, said cap member releasably connected to said lateral walls to define said cavity for connecting said second member to one of the first and second attachment points.
9. The tensioning apparatus of claim 8, wherein said rotatable member is an elongate pin member that is rotatably connected to said first member and that may rotate about a rotational axis that is substantially normal to a longitudinal axis of said pin member, and wherein said surface of said rotatable member that contacts said surface of said second member is an end of said pin member, and further wherein said surface of said second member that is contacted by said end of said pin member is a surface of said cap member.
10. The tensioning apparatus of claim 9, wherein said cap member comprises a first flange that is slidingly movable along a track defined by said first member.
11. The tensioning apparatus of claim 10, wherein said track is partially defined by opposed walls of said first member and wherein said first flange of said cap member is disposed between and may slide along said opposed walls of said first member to assume positions intermediate the object and said substantially normal rotational axis.
12. The tensioning apparatus of claim 11, wherein said first flange of said cap member terminates beyond a space defined between said opposed walls of said first member in a second flange that has a width greater than a distance between said opposed walls of said first member, said second flange retaining said first flange between said opposed walls of said first member.
13. The tensioning apparatus of claim 12, wherein said second flange contacts said first member at one extreme of the range of motion of said first member relative to said second member.
14. The tensioning apparatus of claim 10, further comprising a biasing member for biasing said second member toward said substantially normal rotational axis to thereby urge said surface of said cap member into contact with said end of said pin member.
15. The tensioning apparatus of claim 14, wherein said biasing member is a leaf spring.
16. The tensioning apparatus of claim 15, wherein said leaf spring is connected at a first end to said first member and is connected at a second end to said second member.
17. The tensioning apparatus of claim 15, further comprising a clamping member pivotally secured to said first member for securing a portion of the object thereto, said leaf spring being connected at a second end to said second member and wherein a first end of said leaf spring contacts said clamping member and biases said clamping member to pivot into a desired orientation.
18. The tensioning apparatus of claim 1, wherein the object is an elongate saw blade.
19. The tensioning apparatus of claim 18, further comprising a saw blade chuck connected to said first member for connecting the saw blade to said first member.
20. A tensioning apparatus for placing an object in tension between first and second attachment points, the tensioning apparatus comprising a retention member for coupling the tensioning apparatus to one of the first and second attachment points, the tensioning apparatus further comprising an object attachment member to which the object may be operably connected, said object attachment member being slidably movably connected to said retention member and movable between a tensioning position, in which the object is placed in tension between the first and second attachment points, and a tension releasing position, in which the object is not in tension between the first and second attachment points, said object attachment member having a rotatable member rotatably mounted thereon, said rotatable member comprising a surface that contacts a surface of said retention member during rotation of said rotatable member and urges said object attachment member to slide relative to said retention member from said tension release position into said tensioning position.
21. A tensioning apparatus for placing a saw blade in tension between first and second arms of a scroll saw saw blade yoke, the tensioning apparatus comprising a yoke retention member for coupling the tensioning apparatus to one of the first and second arms, the tensioning apparatus further comprising a saw blade attachment member to which an end of the saw blade may be operably connected, said saw blade attachment member slidingly movably connected to said yoke retention member and movable between a tensioning position, in which the saw blade is placed in tension between the first and second arms, and a tension releasing position, in which the saw blade is not in tension between the first and second arms, said saw blade attachment member having a rotatable member rotatably mounted thereon, said rotatable member comprising a surface that contacts a surface of said yoke retention member during rotation of said rotatable member and urges said saw blade attachment member to slide relative to said yoke retention member from said tension release position toward said tensioning position.
22. A woodworking machine comprising a table for supporting a work piece thereon, a base supporting the work table, a yoke member comprising first and second arms and mounted for pivotal motion on said base, and a motor mounted on said base for driving said yoke member to reciprocate, the woodworking machine further comprising a tensioning apparatus for placing a saw blade in tension between said first and second arms, said saw blade tensioning apparatus comprising a yoke retention member for coupling said saw blade tensioning apparatus to one of said first and second arms, the tensioning apparatus further comprising a saw blade attachment member to which an end of the saw blade may be operably connected, said saw blade attachment member slidingly movably connected to said yoke retention member and movable between a tensioning position, in which the saw blade is placed in tension between said first and second arms, and a tension releasing position, in which the saw blade is not in tension between said first and second arms, said saw blade attachment member having a rotatable member rotatably mounted thereon, said rotatable member comprising a surface that contacts a surface of said yoke retention member during rotation of said rotatable member and urges said saw blade attachment member to slide relative to said yoke retention member from said tension releasing position toward said tensioning position.
23. A tensioning apparatus for placing a saw blade in tension between first and second arms of a scroll saw saw blade yoke, the tensioning apparatus comprising a yoke retention member for coupling the tensioning apparatus to one of the first and second arms, the tensioning apparatus further comprising a saw blade clamping member to which an end of the saw blade may be connected, said saw blade retention member slidingly movably connected to said yoke retention member and movable between a tensioning position, in which the saw blade is placed in tension between the first and second arms, and a tension releasing position, in which the saw blade is not in tension between the first and second arms, said saw blade clamping member having a rotatable member rotatably mounted thereon, said rotatable member comprising a surface that contacts a surface of said yoke retention member during rotation of said rotatable member and urges said saw blade clamping member to slide relative to said yoke retention member from said tension release position into said tensioning position.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US7333898A | 1998-05-05 | 1998-05-05 | |
| US09/073,338 | 1998-05-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2241500A1 true CA2241500A1 (en) | 1999-11-05 |
Family
ID=29418272
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002241500A Abandoned CA2241500A1 (en) | 1998-05-05 | 1998-06-25 | Tensioning apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2241500A1 (en) |
-
1998
- 1998-06-25 CA CA002241500A patent/CA2241500A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |