Patent Application
20060105612
The present invention relates to clamps for securing printed circuit boards during manufacturing processes.
The manufacture of printed circuit (PC) boards typically entails soldering hardware components to a generally planar board. The board is transported along a plurality of stations where different processes are performed on the board and where different components are added to the board, depending upon the intended use of the board. At one station, the soldering station, a mask is disposed over the side of the board that is being printed, and molten solder is spread over the mask, depositing the solder onto the board through openings in the mask. The mask is removed and the board is advanced to the next stations, where other steps, such as the installation of components onto the hot solder, are performed upon the board.
It is important that the board be precisely located at the soldering station so that the solder is accurately deposited onto the board. U.S. Pat. No. 5,899,446 to Thompson discloses a support that uses a vacuum to suck a PC board onto a PC board holder to fixedly secure the PC board during soldering operations. However, such a system requires a sealed environment below the PC board in order to obtain a vacuum, and components on the edges of the bottom face of the PC board may preclude such an environment. Further, such a system is dependent upon the operation of the vacuum system, which may be subject to breakdowns.
U.S. Pat. No. 5,067,648 to Cascini discloses an apparatus for holding a PC board during soldering that requires individual and manual insertion of each PC board into the apparatus, severely limiting the ability to provide mass production of PC boards.
It would be beneficial to provide an apparatus to positively secure a PC board in a predetermined location, while providing the ability to mass produce numerous PC boards in a production line.
Briefly, the present invention provides a PC board clamp. The clamp comprises a base member movable between a first position and a second position, a first lift rail mounted on the base member, and a second lift rail extending generally parallel to the first lift rail. The clamp also includes a first clamping member movably connected to the first lift rail and a second clamping member movably connected to the second lift rail. When the base member is in the first position, the first clamping member is disposed away from the first lift rail and the second clamping member is disposed away from the second lift rail and, when the base member is in the second position, the first clamping member is disposed proximate to the first rail and the second clamping member is disposed proximate to the second lift rail.
Further, the present invention also provides a PC board clamping assembly. The assembly comprises a PC board conveyor rail assembly and a PC board clamp. The rail assembly comprises a first elongated conveyor rail member and a second elongated conveyor rail member spaced apart from the first elongated conveyor rail member. The second elongated conveyor rail extends generally parallel to the first elongated conveyor rail member. The PC board clamp includes a base member movable between a first position and a second position, a first lift rail mounted on the base member and extending generally parallel to the first elongated conveyor rail member, and a second lift rail extending generally parallel to the first lift rail. The PC board clamp also includes a first clamping member movably connected to the first lift rail, and a second clamping member movably connected to the second lift rail. When the base member is in the first position, the first lift rail is disposed below the first conveyor rail member and the second lift rail is disposed below the second conveyor rail member and, when the base member is in the second position, the first lift rail is disposed above the first conveyor rail member and the second lift rail is disposed above the second conveyor rail member.
Also, the present invention provides a method of securing a PC board to a fixture comprising providing a PC board having a top face and a bottom face; delivering the PC board to a predetermined location; engaging the bottom face of the PC board with a lifting device; and lifting the PC board from a first position to a second position, wherein a top clamp engages the top face during the lift between the first position and the second position, such that the PC board is securely retained between the top clamp and the lifting device.
The present invention also provides a method of automatically performing manufacturing processes on a plurality of PC boards comprising providing a first PC board having a top face and a bottom face to a station; delivering the PC board on a conveyor to a predetermined location at the station; engaging the bottom face of the PC board with a lifting device; lifting the PC board from a first position to a second position, wherein a top clamp engages the top face during the lift between the first position and the second position, such that the PC board is securely retained between the top clamp and the lifting device; performing a manufacturing process on the top face; lowering the PC board to the conveyor, wherein the top clamp releases the PC board during the lowering; transporting the PC board away from the station; providing a subsequent PC board to the station; and repeating steps (b) though (h) automatically.
The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. In the drawings:
In the drawings, like numerals indicate like elements throughout. The terminology includes the words specifically mentioned, derivatives thereof and words of similar import. The embodiment illustrated below is not intended to be exhaustive or to limit the invention to the precise form disclosed. This embodiment is chosen and described to best explain the principle of the invention and its application and practical use and to enable others skilled in the art to best utilize the invention.
A clamping assembly 100 for use in securing a PC board 50 in a desired, fixed location is shown in
The conveyor rail assembly 110 may be integrally part of a PC board manufacturing station, while the PC board clamp 140 may be an add-on configuration that may be used to improve the operation of the PC board manufacturing station. Alternatively, the PC board clamp 140 may be constructed integrally with the PC board manufacturing station, as well as the conveyor rail assembly 110.
The PC board 50 has a length “L”, a thickness “W”, and a thickness “T”. The length L, the width W, and the thickness T may vary between PC boards, but the length L is typically between approximately 5.08 cm (2 inches) and 10.16 cm (4 inches), the width W is typically between approximately 10.16 cm (4 inches) and 12.70 cm (5 inches), and the thickness T is typically between approximately 0.10 cm (0.04″) and 0.30 cm (0.12 inches). A common thickness T for the PC board 50 is approximately 0.16 cm (0.06 inches). However, those skilled in the art will recognize that the length L, the width W, and the thickness T may be dimensions outside those specified. The PC board 50 also has a top face 52 and a bottom face 54. Typically, a common surface area of each of the top face 52 and the bottom face 54 is approximately 110 cm2 (15.5 in2).
The conveyor rail assembly 110 includes a first conveyor rail 112 and a second conveyor rail 132. A first conveyor belt 113 comprising a first endless loop extends along the first conveyor rail 112 and a second conveyor belt 133 comprising a second endless loop extends along the second conveyor rail 132. Preferably, the first conveyor belt 113 and the second conveyor belt 133 are each approximately 0.6 cm (0.24 inches) wide. A first end 56 of the PC board 50 rides along the first conveyor belt 113 and a second end 58 of the PC board 50 rides along the second conveyor belt 133 as the conveyor rail assembly 110 transports the PC board 50 into and out of the clamping assembly 100.
The first conveyor rail 112 includes a top face 114 and the second conveyor rail 132 includes a top face 134. The second conveyor rail 132 is parallel to the first conveyor rail 112 and is spaced apart from the first conveyor rail 112 by a predetermined distance D1. Preferably, the distance D1 is slightly less than the length L of the PC board 50 so that the PC board 50 rests on first and second conveyor belts 113, 133, respectively, as shown in
The distance D1 is adjustable by varying the location of the first conveyor rail 112 relative to the second conveyor rail 132. A translational mechanism, such as a screw thread, is used to translate the first conveyor rail 112 to a desired position. The first conveyor rail 112 includes first and second screw blocks 116, 118, respectively, that are disposed beneath and connected to the first conveyor rail 112. A screw 120, 122 is threaded through each screw block 116, 118, respectively. Each screw 120, 122 includes a first end 120a, 122a, respectively that is operatively connected to a drive mechanism 124 and a second end 120b, 122b that is rotatably supported to allow each screw 120, 122 to rotate with the drive mechanism 124. Preferably, the drive mechanism 124 is an electric motor, although those skilled in the art will recognize that other drive mechanisms, such as a hand crank, may be used instead of a motor. As seen in
The first conveyor rail 112 also includes first and second bearing blocks 126a, 126b, respectively, that are each disposed beneath and connected to the first conveyor rail 112. Each bearing block 126a, 126b is slidingly disposed along a rail 128a, 128b, respectively, to support the first conveyor rail 112 and to maintain the parallel relationship of the first conveyor rail 112 relative to the second conveyor rail 132 during and after movement of the first conveyor rail 112.
The PC board clamp 140 includes a tooling support table 142 extending in a plane “P”, that is movably disposed below the conveyor rails 112, 132. The tooling support table 142 is movable between a first, or lower position, as shown in the end view of the assembly 100 in
The clamp 140 further includes a first board lift member 150 that includes a first base portion 152 and a first lift rail 154 that extends upward from the first base portion 152. The first board lift member 150 is disposed generally between the first conveyor rail 112 and the second conveyor rail 132. The first lift rail 154 preferably has a cross section of approximately 0.10 cm (0.04 inches). The first lift rail 154 supports the first end 56 of the PC board 50 during lifting and manufacturing operations. As seen in
The clamp 140 also includes a second board lift member 160 that includes a second base portion 162 and a second lift rail 164 that extends upward from the second base portion 162. The second board lift member 160 is disposed generally between the first conveyor rail 112 and the second conveyor rail 132. The second lift rail 164 preferably has a width of approximately 0.10 cm (0.04 inches). The second lift rail 164 supports the second end 58 of the PC board 50 during lifting and manufacturing operations. Similar to the first board lift member 150, the second board lift member 160 may include the second lift rail 164 being a separate component from the second base portion 162, with the second lift rail 164 being fixedly connected to the second base portion 162, such as by a screw connection. However, those skilled in the art will recognize that the second lift rail 164 may be integrally manufactured as an extension of the second base portion 162. In a preferred embodiment, the second base portion 162 is constructed from aluminum or other suitable material, while the second lift rail 164 is constructed from stainless steel, nickel, or some other suitable material that is connected to the second base portion 162 with a screw connection.
The second lift rail 164 is generally parallel to the first lift rail 154 and extends a distance D2 away from the first lift rail 154 a distance that is at least slightly less than the length L of the PC board 50 so that the first and second lift rails 154, 164 can support the PC board 50. As seen in
Further, as seen in
Referring to
A bottom portion of each guide post 157a, 157b is connected to a base 159a, 159b that is connected to the first base member 152. The bases 159a, 159b may be constructed separately from the first base member 152 and then fixedly connected to the first base member 152, such as by a threaded connection, or the bases 159a, 159b may alternatively be constructed integrally with the first base member 152. When the tooling support table 142 is in the lowered position, the guide posts 157a, 157b maintain the bases 159a, 159b and the first base member 152 approximately 0.127 cm (0.050 inches) above the tooling support table 142 to enable the bases 159a, 159b and the first base member 152 to traverse the tooling support table 142 during operation of the drive mechanism 124.
Each base 159a, 159b also includes a clamp support post 170a, 170b. The clamp support posts 170a, 170b each extend upward from the bases 159a, 159b, respectively, generally parallel to the guide posts 157a, 157b. The clamp support posts 170a, 170b support a first clamp rail 172 that extends parallel to the first conveyor rail 112. The first clamp rail 172 is situated such that the first conveyor rail 112 is disposed generally between the first lift rail 154 and the first clamp rail 172. The first clamp rail 172 includes two through holes 174a, 174b that are sized to allow clamp posts 176a, 176b to slide along the through holes 174a, 174b, respectively, with minimal resistance. The clamp posts 176a, 176b support a first clamp 179. Each clamp post 176a, 176b also includes a C-clip 180a, 180b, respectively, disposed at a lower end of each clamp post 176a, 176b. A helical spring 181a, 181b is disposed around each respective clamp post 176a, 176b between the C-clip 180a, 180b and the first clamp rail 172. The helical springs 181a, 181b bias the first clamp 179 toward the first clamp rail 172 and allow the first clamp 179 to travel approximately 2.54 cm (1 inch). The first clamp 179 includes a first lip 182 that extends from the top of the first clamp 179 generally toward the second conveyor rail 132. Preferably, the first lip 182 is approximately 0.018 cm (0.007 inches) thick and constructed from stainless steel. The first clamp 179 includes an elongated first steel stock 179a that is embedded in the first clamp 179. The first steel stock 179a is releasably connected to the first clamp 179, such as by screws (not shown). The first lip 182 is fixedly connected to the first steel stock 179a so that the first lip 182 may be readily replaced by removing the first steel stock 179a from the first clamp 179 and replacing with a replacement steel stock (not shown).
Referring back to
The distance between the first and second lips 182, 194, respectively is at least slightly less than the length L of the PC board 50, as is shown in
Optionally, a compliant locking support fixture, such as the fixture disclosed in U.S. Pat. No. 6,702,272 to Moncavage, may be disposed on the tooling support table 142 between the first and second base portions 152, 162, respectively, and used to support the PC board 50 from underneath during the soldering process. However, those skilled in the art will recognize that other methods for supporting the PC board 50 from underneath may be used and that, for particularly small PC boards, the support from underneath may be omitted entirely.
Prior to operation of the PC board clamp 140, the spacing of the conveyor rails 112, 132 are set by operating the drive mechanism 124. The drive mechanism 124 rotates the screw 120, which in turn rotates the screw 122 via the endless loop 125. The screws 120, 122 rotate in the same direction, driving the screw blocks 116, 118 in a desired direction, either toward or away from the second conveyor rail 132. Since the screw blocks 116, 118 are fixedly connected to the first conveyor rail 112, the first conveyor rail 112 is thusly moved either toward or away from the second conveyor rail 132. The bearing blocks 126a, 126b also travel with the first conveyor rail 112. Since the first base portion 152 is operatively connected to the bearing blocks 126a, 126b through the bearing block mounts 127a, 127b, the guide posts 157a, 157b and their respective bases 159a, 159b, the first base portion 152 also moves with the first conveyor rail 112. At this time, the tooling support table 142 is in a lowered position, and the first base portion 152 and the 159a, 159b are suspended above the tooling support table 142 and are free to move over the tooling support table 142 without interference.
When the conveyor rails 112, 132 are spaced apart such that the distance between the first conveyor rail 112 and the second conveyor rail 132 is slightly smaller (approximately 0.3 cm), than the length L of the PC board 50, the drive mechanism 124 is stopped. The PC board 50, or a series of PC boards 50, all having the same length L, are able to be loaded onto the conveyor assembly 110, from the lower left hand side of the page of
At this time, the tooling support table 142 is in a lowered position, as shown in
When the PC board 50 travels to a predetermined position between the first and second lift rails 154, 164 and the first and second lips 182, 194, respectively, the conveyor assembly 110 stops. The tooling support table 142 is vertically translated toward PC board 50 by activating the lift screw 144. Since the second base portion 162 is already disposed on the tooling support table 142, the second base portion 162 begins to move upward with the tooling support table 142. The tooling support table 142 traverses the space between the tooling support table 142 and the bottom of the first base portion 152 and the bases 159a, 159b and begins to lift the first base portion 162 and the bases 159a, 159b toward the PC board 50.
As the base portions 152, 162 are further lifted, the lift rails 154, 164 engage the PC board 50 at the bottom face 54 proximate to each of the first and second ends 56, 58, respectively, and lift the PC board 50 from the conveyor rails 112, 132. As the tooling support table 142 is further lifted toward the PC board 50, the clamp rails 172, 186 are lifted upward with the tooling support table 142. However, the clamps 179, 191 remain seated on top of their respective conveyor rails 112, 132, as the clamp posts 176a, 176b, 190a, 190b slide through their respective through holes 174a, 174b, 188a, 188b as the tooling support table 142 is being lifted.
When the first and second lift rails 154, 164 engage the bottom face 54 of the PC board 50, the first and second lift rails 154, 164 lift the PC board 50 from the conveyor rails 112, 132. The first and second lift rails 154, 164 lift the PC board 50 until the top face 52 of the PC board 50, proximate to each of the first and second ends 56, 58, respectively, engages each of the first and second lips 182, 194 of the first and second clamps 179, 191, respectively. The springs 180a, 180, 192a, 192b bias the respective first and second clamps, 179, 191 toward a downward position, clamping the PC board 50 between the first and second clamps 179, 191 and the first and second lift rails 154, 164, securing the PC board 50 in the clamp 140. When the PC board 50 is securely clamped to the board clamp 140, the lift screw 144 stops to allow a camera (not shown) to enter the space between the PC board 50 and the processing station 62 to confirm proper alignment of the PC board 50 with respect to the processing station 62. If the PC board 50 is not properly aligned with the processing station 62, the processing station 62 may self-adjust to provide proper alignment. Alternatively, the clamping assembly 100 may self-adjust via x, y, and theta positioning hardware (not shown) in order to provide proper alignment of the PC board 50 with the processing station 62.
After the camera confirms proper location of the PC board 50 with respect to the processing station 62, the lift screw 144 reactivates, and the first and second lift rails 154, 164 continue to lift the PC board 50 upward to the processing station 62, where a manufacturing step, such as solder application, is performed on the PC board 50.
After the manufacturing step is performed on the PC board 50, the lift screw 144 lowers the tooling support table 142 back toward the initial position. The first and second clamps 179, 191 are lowered onto the first and second lift rails 112, 132, respectively, and the PC board 50 is released from the clamp lips 182, 194. The first and second lift rails 154, 164 continue to lower the PC board 50 until the PC board 50 is lowered onto the first and second conveyor belts 113, 133. The lift screw 144 continues to lower the tooling support table 142 until the tooling support table 142 returns to its original position. The conveyor assembly 110 transports the PC board 50 away from the clamping assembly 100 and to the next station in line for manufacturing. The next PC board 50 is delivered to the clamping assembly 100 by the first and second conveyor belts 113, 133, and the process is repeated for the next PC board 50.
Preferably, the cycling time of the conveyor assembly 110 and the clamping assembly 100 between adjacent PC boards 50 in a production run is between approximately 2 and 4 seconds, and ore preferably, approximately 3 seconds, although those skilled in the art will recognize that the cycling time may be more or less than that timeframe.
Preferably, the clamping assembly 100 is electronically connected to a controller (not shown) such that the conveyor rail assembly 110 and the lift screw 144 automatically operate to transport PC boards 50 to the PC board clamp 140, to lift each PC board 50 from the conveyor rail assembly 110 to the processing station 62 for operation, to lower each PC board 50 back to the conveyor rail assembly 110, and to transport each PC board 50 to the next station for operation.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
