Patent Grant
7108255
The present invention relates to a device for reducing a velocity of a piston within a cylinder. More specifically, the present invention relates to a cushioning pin for limiting a flow through an orifice within a pneumatic device.
Automated pneumatic clamping devices are commonly utilized in manufacturing environments to secure a workpiece, such as a sheet metal part, to a base for processing, such as welding, punching, or assembly with other parts. Generally, conventional clamping devices comprise a piston and cylinder, wherein the piston is operable to translate within the cylinder in order to force a clamping member to rotate about an axis.
Typically, the clamping member 12 is considered a wearable part, wherein the clamping member is replaced regularly. The clamping member 12 of the prior art, however, has typically been fairly difficult to remove from the housing 14, because a removal of several other components associated with the clamping member is typically required prior to the removal of the clamping member. Conventionally, the fixed pivot pin 16 is generally fixed to the housing 14 and the clamping member 12 is generally coupled to the pivot pin 16 via a hole 30 in the clamping member. Such a pin and hole arrangement, therefore, typically requires the pivot pin 16 to be removed from the housing 14 in order to remove and replace the clamping member 12. Furthermore, other components such as a location pin 32, and/or other components are also typically removed prior to the removal of the clamping member 12 from the housing 14. Removal of such components can increase maintenance time and cost associated with the prior art clamping mechanism 10.
Furthermore, many applications exist wherein the workpiece 18 comprises an upward-facing flange 34, and wherein a locking arm 36 associated with the clamping member 12 must clear the flange, yet still provide an adequate clamping force to the workpiece. The presence of the flange 34 can cause difficulties when dealing with conventional clamping mechanisms, since the conventional clamping mechanisms are generally limited to the fixed axis 28 of rotation of the clamping member 12.
Still further, typical pneumatic clamping devices of the prior art operate via a gas pressure (e.g., 60 PSI or greater) being applied to a first portion 38 or a second portion 40 of the cylinder 22 via a respective first port 42 or second port 44 which is in fluid communication with the cylinder. The piston 24 is generally forced by the gas pressure between a first position 46 and a second position 48 within the cylinder 22, depending on which of the first port 42 or the second port 44 is pressurized. Gas which resides in the second portion 38 of the cylinder 22, for example, is generally exhausted to atmosphere via the second port 44 upon an application of the gas pressure to the first port 42, thus causing the piston 24 to translate from the first position 46 to the second position 48. In general, a velocity of the piston 24 translating within the cylinder 22 rapidly accelerates upon the application of gas pressure to either of the first port 42 or the second port 44, and rapidly decelerates once the piston has reached an end 50 of the cylinder.
The travel seen by the piston 24 between the ends 50 of the cylinder 22 generally defines a stroke S of the piston. Typically, the rapid deceleration at the end of the stroke S of the piston 24 can produce unwanted impact forces, both to components of the pneumatic device 10 such as the piston 24, cylinder 22, drive pin 26, and clamping member 12, as well as undesirable forces exerted on the workpiece 18, wherein undesirable effects such as deformations or dimples may result in the workpiece. Conventional attempts to minimize the impact forces at the ends of the stroke S have included, for example, cushioning devices, such as a “snubber”. A typical snubber 52 illustrated in
Therefore, a need exists for a clamping fixture which provides for easy removal of the clamping member from the fixture, as well as a need for a simple apparatus for minimizing impact forces seen in pneumatic devices.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention is directed toward a device for locating and clamping a workpiece. According to one exemplary aspect of the present invention, a locating and clamping fixture is disclosed, wherein the locating and clamping fixture comprises a generally hollow body and a floating clamping arm, wherein the floating clamping arm is generally easily removable from the hollow body. The fixture, for example, further comprises a first cam follower located within the hollow body and a drive pin operable to translate along a first axis associated therewith. The drive pin further comprises a second cam follower, wherein the second cam follower is further operable to translate along the first axis in conjunction with the translation of the drive pin.
The floating clamping arm disclosed in the present invention comprises a first cam surface, a second cam surface, and a gripping portion, wherein the first cam surface and the second cam surface, for example, are operable to respectively engage the first cam follower and the second cam follower. The first cam surface and the second cam surface, for example, are generally open-looped in configuration, wherein the first cam follower and the second cam follower are operable to be disengaged from the first cam surface and the second cam surface, respectively.
The drive pin is further operable to provide a driving force to the clamping arm, wherein upon an application of the driving force to the clamping arm, the clamping arm is operable to rotate and linearly translate with respect to the body. The gripping portion of the clamping arm, for example, is further operable to extend over the workpiece, wherein the gripping portion is operable to generally clamp the workpiece to the body.
According to another exemplary aspect of the present invention, the locating and clamping fixture further comprises a locating pin, wherein the locating pin is operable to generally locate the workpiece with respect to the hollow body. The locating pin, for example, is generally hollow, and comprises an aperture therethrough, wherein the gripping portion of the floating clamping arm is operable to selectively translate through the aperture upon the application of the driving force.
In accordance with yet another exemplary aspect of the present invention, an anti-rotation mechanism is provided, wherein the anti-rotation mechanism generally limits a rotation of the drive pin with respect to the hollow body. According to another exemplary aspect of the present invention, a piston and cylinder are associated with the hollow body, wherein the piston is operably coupled to the drive pin, and wherein an application of compressed gas within the cylinder is operable to translate the piston with respect to the cylinder, thereby providing the driving force.
According to still another exemplary aspect of the present invention, the locating and clamping fixture comprises a locking mechanism, wherein upon a loss of the driving force, the locking mechanism is operable to generally maintain a position of the floating clamping arm with respect to the body. The drive pin, for example, comprises a driver portion and a driven portion, wherein the driver portion and the driven portion are operable coupled to one another. The locking mechanism, for example, comprises one or more rollers associated with the body, the driver portion and the driven portion of the drive pin, wherein, the one or more rollers are generally operable to selectively translate within the body, as well as to selectively limit a translation of the clamping arm, depending on a position of the drive pin.
Furthermore, in accordance with another exemplary aspect of the present invention, a cushioning mechanism is disclosed, wherein the cushioning mechanism is operable to limit an impact force associated with a piston within a cylinder. For example, the cushioning mechanism comprises one or more cushioning pins associated with the piston, and one or more respective cushioning holes associated with the cylinder. The one or more cushioning holes, in conjunction with the one or more respective cushioning pins, for example, are operable to generally selectively limit a fluid communication between an interior portion of the cylinder with one or more respective ports associated with the cylinder. The one or more cushioning pins, for example, are operable to translate into and out of the one or more cushioning holes, wherein a flow of compressed gas between the interior portion of the cylinder and the one or more ports is generally limited by the cushioning pins, depending on the location of the piston with respect to the cylinder.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
The present invention will be described with reference to the drawings wherein like reference numerals are used to refer to like elements throughout. It should be understood that the description of these aspects are merely illustrative and that they should not be taken in a limiting sense. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident to one skilled in the art, however, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate description of the present invention.
The present invention is directed towards a fixture for positionally locating and clamping a workpiece to a surface. The fixture, for example, comprises a clamping arm operable to clamp the workpiece to the surface, wherein the clamping arm is easily removable from the fixture. Furthermore, the present invention is directed towards a cushioning apparatus, wherein the cushioning apparatus may be utilized in the locating and clamping fixture, and wherein the cushioning apparatus generally reduces a velocity of a piston translating within a cylinder associated with the fixture.
Referring now to the figures,
According to another exemplary aspect of the invention, the locating pin 120 comprises a generally hollow portion 122 and an aperture 123 therethrough, wherein at least another portion 124 of the clamping arm 115 is operable to generally reside within the hollow portion. Alternatively, the locating pin 120 may comprise one or more guide members (not shown), wherein the one or more guide members are operable to generally locate the workpiece 105 with respect to the fixture 100.
In accordance with another aspect of the present invention, the locating pin 120 is operable to generally maintain a horizontal spatial position of the workpiece 105 with respect to the fixture 100. According to one exemplary aspect of the invention, the workpiece 105, may comprise a flange 107 associated with the hole 106, wherein the flange extends outwardly from a surface 108 of the workpiece by a predetermined amount (e.g., a flange extending about 2–3 mm vertically from the surface of the workpiece) around a diameter of the hole. Such flanges 107, for example, are commonly found in workpieces 105 such as automotive components, wherein the flange generally provides rigidity and/or additional structural integrity to the workpiece.
According to another exemplary aspect of the present invention, the clamping arm 115 is operable to secure the workpiece 105 relative to the fixture 100. The clamping arm 115, for example, comprises a gripping portion 125 at a distal end 128 thereof, wherein the clamping arm is operable to generally maintain a vertical spatial position of the workpiece 105 with respect to the fixture 100. The clamping arm 115 is generally operable to clamp the workpiece 105 between the gripping portion 125 and a base portion 129 of the fixture, wherein the base portion is associated with the one or more of the body 110 and the locating pin 120. According to one example, the base portion 129 is integral to the locating pin 120. According to another example, the base portion 129 is integral to the body 110. The gripping portion 125 of the clamping arm 115, for example, is generally U-shaped, wherein an end surface 130 of the gripping portion is operable to engage the surface 108 of the workpiece 105, and wherein the generally U-shaped gripping portion is operable to generally straddle the flange 107, thereby limiting contact between the clamping arm and the flange.
According to yet another example, the gripping portion 125 of the clamping arm 115 is operable to translate through the aperture 123 in the locating pin 120. The fixture 100 of
According to another exemplary aspect of the present invention, the fixture 100 further comprises a drive pin 135, wherein the clamping arm 115 is generally coupled to the drive pin. The drive pin 135 is operably to linearly translate within the body 110 along a first axis 136, wherein the translation of the drive pin is associated with a predetermined movement of the clamping arm 115, as will be discussed infra. The drive pin 135, for example, is further operably coupled to a piston 140, wherein the piston is operable to linearly translate along the first axis 136 within a cylinder 145. According to one example, the cylinder 145 is separately mounted to the body 110, wherein the cylinder can be separated from the body by a removal of one or more fasteners (not shown). Alternatively, the cylinder 145 may be integral to the body 110 of the fixture 100, wherein a bore (not shown) within the body generally defines the cylinder.
The translation of the piston 140 within the cylinder 145, for example, is operable to provide a driving force F to the drive pin 135, wherein the driving force is operable to cause the drive pin to linearly translate along the first axis 136 within the body 110. As an alternative, the piston 140 and cylinder 145 may be replaced by a servo motor (not shown) or other electromechanical, pneumatic, or hydraulic mechanism which is operable to provide the driving force F to the drive pin 135. Accordingly, any mechanism operable to provide the driving force F to the drive pin 135 is contemplated as falling within the scope of the present invention.
According to another exemplary aspect of the invention, the fixture 100 further comprises a first cam follower 1,50 and a second cam follower 155, wherein the first cam follower is associated with the body 110, and wherein the second cam follower is associated with the drive pin 135. One or more of the first cam follower 150 and second cam follower 155, for example, may comprise a cylindrical pin or a roller bearing, wherein the first cam follower and the second cam follower are substantially resistant to frictional wear. The first cam follower 150, for example, is generally fixed with respect to the body 110, while the second cam follower 155 is generally fixed with respect to the drive pin 135. The second cam follower 155 is furthermore moveable with respect to the body 110 along the first axis 136 in conjunction with the translation of the drive pin 135. Still further, the drive pin 135, and hence the second cam follower 155, are moveable between an extended position 156 (e.g., as illustrated in
In accordance with yet another exemplary aspect of the present invention, the clamping arm 115 comprises a floating clamping arm 160, wherein the floating clamping arm is operable to be easily removed from the fixture 100. The floating clamping arm 160, for example, comprises a first cam surface 165 and a second cam surface 170, wherein the first cam follower 150 is operable to engage the first cam surface, and wherein the second cam follower 155 is operable to engage the second cam surface. The first cam surface 165 and the second cam surface 170, for example, are arranged such that upon the translational movement of the drive pin 135 (and hence, the translational movement of the second cam follower 155 with respect to the body 110), the floating clamping arm 160 is operable to linearly translate and rotate with respect to the body 110. The floating clamping arm 160 is, therefore, positionable within the body 110 via the translation of the drive pin 135 between the extended position 156 of
The clamping arm 160, for example, is not rigidly fixed to either of the first cam follower 150 or the second cam follower 155, wherein the first cam surface 165 and the second cam surface 170 are operable to both linearly translate and to rotate with respect to each of the first cam follower and the second cam follower. Therefore, floating clamping arm 160, for example, may be manually maneuvered between the first cam follower 150 and the second cam follower 155 in the absence of the driving force F. Furthermore, the floating clamping arm 160 can be easily removed from the body 110, as will be described infra.
Referring again to
The first dowel pin 185, for example, is associated with the locating pin 120, wherein the first dowel pin is operable to generally limit the rotation of the floating clamping arm 160 with respect to the body. In accordance with one example, the first dowel pin 185 extends downward into the generally hollow body 110 from the locating pin 120, wherein the first dowel pin is generally fixed with respect to the locating pin. The first dowel pin 185, for example, is operable to generally limit the rotation of the floating clamping arm 160 within the body 110, wherein the sliding surface 180 associated with the floating clamping arm is operable to slidingly contact the first dowel pin, thus limiting the rotation of the floating clamping arm, yet allowing the floating clamping arm to generally translate along, or parallel to, the first axis 136.
According to still another exemplary aspect of the present invention, the fixture 100 further comprises an anti-rotation mechanism 190 operatively associated with the drive pin 135. The anti-rotation mechanism 190 generally limits a rotation of the drive pin 135 with respect to the body 110. According to one example, the piston 140 and cylinder 145 are generally ovular when viewed perpendicular to the first axis 136, wherein the generally ovular piston and cylinder generally define the anti-rotation mechanism 190. Another exemplary anti-rotation mechanism 190 comprises one or more splines (not shown) associated with the drive pin 135 and the body 110, wherein the one or more splines generally engage one another to generally permit a translation of the drive pin with respect to the body along the first axis 136, while generally limiting a rotation of the drive pin with respect to the body about the first axis. Other anti-rotation mechanisms 190 such as pins (not shown) and corresponding slots (not shown) or any other device which generally limits the rotation of the drive pin 135 with respect to the body 110 are furthermore contemplated, and fall within the scope of the present invention.
According to another exemplary aspect of the present invention, the fixture 100 comprises a first port 192 and a second port 194 associated with a respective first end 196 and second end 197 of the cylinder 145. The first port 192 and the second port 194 are operable to generally permit a selective flow of compressed gas (not shown) from a compressed gas source (not shown) therethrough. The first port 192 and the second port 194, for example, are furthermore operable to selectively vent compressed gas from the cylinder 145. The selective flow of compressed gas through one of the first port 192 or the second port 194 to an interior portion 198 of the cylinder 145, for example, is operable to selectively translate the piston 140 within the cylinder, depending on which of the first port or the second port receives the compressed gas and which of the first port or the second port vents the compressed gas to atmosphere. Upon receiving the flow of compressed gas to the first port 192 or the second port 194, the respective first end 196 or second end 197 of the cylinder 145 becomes pressurized, and the other one of first port or the second port is operable to vent the compressed gas to atmosphere from the respective first end or second end of the cylinder, thereby causing the translation of the piston 140 along the first axis 136 due to a differential in pressure.
In accordance with another exemplary aspect of the present invention,
In accordance with another exemplary aspect of the present invention, the floating clamping arm 160 can be easily removed from the fixture 110 without removing the first cam follower 150 or the second cam follower 155 from the body 110. For example, referring again to
It should also be noted that the floating clamping arm 160 of the present invention may be associated with a fixture 100 which does not comprise the locating pin 120 as mentioned above. For instance, the gripping portion 125 of the floating clamping arm 160 can extend outwardly from the body 110, wherein the workpiece 105 can be generally clamped between the gripping portion 125 of the clamping arm 160 and the body 110, and wherein the first sidewall 199 is associated with the body. Furthermore, the first dowel pin 185 can be associated with the body 110 (e.g., a removable pin or block removably attached to the body), rather than being associated with the locating pin assembly 120.
In accordance with still another exemplary aspect of the present invention, as illustrated in
The locking mechanism 210, for example, comprises the drive pin 135 being separated into two segments; namely, a driver portion 215 coupled to the piston 140 and a driven portion 220 coupled to the clamping arm 115. The driven portion 220, for example, comprises a generally hollow outer shaft 225, and the driver portion 215 comprises a generally solid inner shaft 226, wherein the driver portion 215 is operable to translate within the driven portion 220 along the first axis 136. The driver portion 215 and the driven portion 220 of the drive pin 135, for example, are operably coupled to one another by a second dowel pin 230 associated with the driver portion, and a first slot 235 associated with the driven portion, wherein the second dowel pin is operable to translate along the first axis 136 between extents 240 associated with the first slot 235. The first slot 235 and second dowel pin 230, for example, are operable to provide a “rap” feature, where the driver portion 215 is operable to translate while the driven portion 220 remains generally stationary, and wherein the driver portion is operable to gain momentum prior to reaching one of the extents 240 of the first slot 235. A gain in momentum prior to engaging the driven portion 220 is advantageous in that inertial forces associated with the clamping arm 115 or other components can be overcome by the momentum gained in the driver portion 220.
The locking mechanism 210 may further comprise one or more rollers 245, wherein the one or more rollers are operable to maintain a position of the clamping arm 115 in a case where the driving force F is lost. For example, the driver portion 215 of the drive pin 135 comprises an annular groove 250 at a one end 252 thereof, wherein a radius RAG of the annular groove is associated with a radius RR of the one or more rollers 245, and a width WAG of the annular groove is slightly less than twice the radius RR of the one or more rollers. Furthermore, the body 110 comprises one or more lateral grooves 255 perpendicular to the first axis 136 and offset a predetermined amount from the first axis, wherein a radius RLG of the one or more lateral grooves is further associated with the radius RR of the one or more rollers 245, and a width WLG of the lateral groove is slightly less than twice the radius RR of the one or more rollers.
Still further, the driven portion 220 of the drive pin 135 further comprises one or more channels 260 therein, wherein the one or more channels are associated with the respective one or more rollers 245. Each of the one or more channels 260 has a generally rectangular cross section when viewed perpendicularly to the first axis 136, wherein a width WC of the one or more channels is slightly more than twice the radius RR of the one or more rollers 245. The one or more channels 260, for example, are generally eccentric to the driven portion 220 of the drive pin 135 and are generally parallel to one or more rollers 245.
The one or more rollers 245 are furthermore associated with the annular groove 250, the one or more lateral grooves 255, and the one or more channels 260, wherein, depending upon a position of the driven portion 220 with respect to the body 110 along the first axis 136, the one or more rollers 245 may reside within one or more of the annular groove 250, the one or more lateral grooves 255, and the one or more channels 260. The locking mechanism 210, for example, still further comprises the driven portion 220 of the drive pin 135 having a second slot 265 therein, wherein the second slot is generally parallel with the first axis 136 and radially offset from the first slot 235 by a predetermined amount (e.g., approximately 90 degrees about the first axis). Accordingly, the locking mechanism 210 yet further comprises a third dowel pin 270 associated with the body 110, wherein an end portion 275 of the third dowel pin is operable to reside within the second slot 265. The third dowel pin 270, for example, generally permits the driven portion 220 of the drive pin 135 to translate between a first extent 280 and a second extent 285 of the second slot 265.
In operation, the locking mechanism 210, for example, is operable to generally maintain the position of the clamping arm when the driving force F is lost by an interface between the one or more rollers 245, the drive pin 135, and the one or more lateral grooves 255.
During the translation illustrated in
According to another exemplary aspect of the present invention, the locking mechanism 210 further comprises a resilient member 292, a ball 294, and one or more secondary grooves 296 associated with the driven member 220. The resilient member 292 (e.g., a resilient polyurethane cylinder or a spring) and the ball 294 generally reside within a cylindrical bore 297 in the body 110, wherein the ball is operable to selectively engage the one or more secondary grooves, depending on the position of the driven portion 220. For example, the driven portion comprises secondary grooves 296A and 296B associated with the extended position and the retracted position of the drive pin 135, respectively. The ball 294 is operable to engage secondary groove 296A when the drive pin 135 (and hence, the driven portion 220) is in the extended position, and is further operable to engage secondary groove 296B when the drive pin is in the retracted position. The ball 294 engaging the one or more secondary grooves 296 generally provides a limited force for maintaining the position of the driven portion 220 with respect to the body.
According to yet another exemplary aspect of the present invention, one or more cushioning pins 300 are associated with the piston 140, wherein the one or more cushioning pins are operable to generally reduce a velocity of the piston with respect to the cylinder 145. The one or more cushioning pins 300, for example, are generally rigidly mounted to the piston 140, wherein the one or more cushioning pins are operable to translate with the piston 140 with respect to the cylinder 145. Each of the one or more cushioning pins is operable to linearly translate between an associated first position 305 (e.g., the extended position illustrated in
As illustrated in
An application of compressed gas to the first port 192 while venting the second port 194 to atmosphere, for example, will create a compressive force on the cushioning pin 315B and the piston 140, wherein the piston is generally forced downward by the compressed gas, thereby forcing the cushioning pin 300B from the cushioning hole 315B. Upon the application of the compressed gas to first port 192 (with second port 194 vented to atmosphere), the piston 140 is generally forced to the second position 310, as illustrated in
During a transition between the first position 305 of
Although the invention has been shown and described with respect to certain aspects, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (systems, devices, assemblies, etc.), the terms used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure that performs the function in the herein illustrated exemplary aspects of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several aspects, such feature may be combined with one or more other features of the other aspects as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the term “includes” is used in either the detailed description and the claims, such term is intended to be inclusive in a manner similar to the term “comprising.”
This application is a continuation of U.S. patent application Ser. No. 10/454,170 filed Jun. 4, 2003 now U.S. Pat. No. 6,931,950, which is entitled “Cushioning Pin for Pneumatic Device”, which claims priority to U.S. Provisional Patent Application Ser. No. 60/456,830 filed Mar. 21, 2003, which is entitled “Cushioning Device for Piston and Cylinder”.
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| Number | Date | Country | |
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| Parent | 10454170 | Jun 2003 | US |
| Child | 11155806 | US |
