Pneumatic fixture clamp

According to one aspect, a pneumatic fixture clamp includes a housing having a rotational axis and a housing exterior surface. The housing exterior surface includes a workpiece engagement surface intersected by the rotational axis and configured for engaging a workpiece assembly, and a turntable engagement surface disposed on a side of the housing opposite the workpiece engagement surface, intersected by the rotational axis, and configured for engaging a turntable of a machine center. A chamber is defined in the housing between the workpiece engagement surface and the turntable engagement surface along the rotational axis. A piston slidably disposed in the chamber and configured for being driven between an extended position and a retracted position relative to the chamber. A fluid passage is defined in the housing, connected to the chamber, and configured for providing fluid from a fluid line to the chamber.

BACKGROUND

Conventional work holders for machine tools are generally designed to provide sufficient clamping force so that the cutting element will not displace the workpiece, and in many cases are pneumatically controlled. However, the pneumatic controls of conventional work holders are often bulky, difficult to install, or are otherwise incompatible with a work space provided in a five axis machining center. For example, as shown inFIG. 1of the present application, U.S. Pat. No. 5,743,687 discloses a pneumatic, rotatable clamp which enables a work holder to secure a fixture and workpiece. In its disclosure, U.S. Pat. No. 5,743,687 provides a clamp and a pneumatic servomechanism separately disposed at opposite sides of a turntable, with the servomechanism extended behind the turntable. Notably, if this construction were employed in a five axis machining center having a turntable that pivots about more than one axis, the servomechanism disclosed in U.S. Pat. No. 5,743,687 would swing behind the turntable and cause interference between at least the servomechanism including associated air conduits, and supporting features of the machining center located behind the turntable at various rotated positions of the turntable.

SUMMARY

According to one aspect, a pneumatic fixture clamp includes a housing having a rotational axis and a housing exterior surface. The housing exterior surface includes a workpiece engagement surface intersected by the rotational axis and configured for engaging a workpiece assembly, and a turntable engagement surface disposed on a side of the housing opposite the workpiece engagement surface, intersected by the rotational axis, and configured for engaging a turntable of a machining center. A chamber is defined in the housing between the workpiece engagement surface and the turntable engagement surface along the rotational axis. A piston is slidably disposed in the chamber and configured for being driven between an extended position and a retracted position relative to the chamber. A drawbar has a proximal end connected with the piston such that the piston is configured for driving the drawbar between an extended state and a retracted state of the drawbar which respectively correspond with the extended position and the retracted position, and has a distal end connected to a clamping mechanism configured for releasably engaging a workpiece assembly. A fluid passage is defined in the housing, connected to the chamber, and configured for providing fluid from a fluid line to the chamber so as to drive the piston from the extended position toward the retracted position. A first fluid passage section is formed in the fluid passage, extending from the chamber and in fluid communication with the housing exterior surface, and a second fluid passage section is formed in the fluid passage, extending from the housing exterior surface and in fluid communication with the first fluid passage section.

DETAILED DESCRIPTION

FIG. 2depicts a pneumatic fixture clamp100installed on a machining center102. The pneumatic fixture clamp100is supported on a turntable104of the machining center102and configured for securing a workpiece assembly110relative to the machining center102. As depicted, the machining center102is configured to rotate a housing112of the pneumatic fixture clamp100with the turntable104about a first rotational axis114and a second rotational axis116orthogonal to the first rotational axis114. Each of the first rotational axis114and the second rotational axis116have directions respectively defined by bearings that support the turntable104in the machining center102. The housing112is positioned on the turntable104, centered on the first rotational axis114such that a longitudinal axis of the housing112is collinear with the first rotational axis114. With this construction, when the turntable104and by extension the housing112is in an upright position with respect to the machining center102as shown inFIG. 2, the first rotational axis114is vertical and the second rotational axis116is horizontal.

FIG. 3depicts the pneumatic fixture clamp100including the housing112, with a housing exterior surface120featuring a work engagement surface122and a turntable engagement surface124. The work engagement surface122is a top surface of the housing112when the housing112is oriented in the upright position, and is configured for engaging the workpiece assembly110. The workpiece assembly110includes at least a workpiece (not shown) and may further include a fixture, workholding device, or adaptor (not shown) configured for supporting the workpiece on the work engagement surface122. As such, the work engagement surface122may receive a workpiece directly, or receive a fixture, workholding device, or adaptor configured for supporting the workpiece on the work engagement surface122. The turntable engagement surface124is disposed on a side of the housing112opposite the work engagement surface122, is intersected by the first rotational axis114and is configured for engaging the turntable104of the machining center102.

A chamber130is defined in the housing112between the work engagement surface122and the turntable engagement surface124along the first rotational axis114. The housing112is formed from a housing top portion132located above the chamber130when the housing112is oriented in the upright position, extending from the chamber130to the work engagement surface122; a housing wall portion134disposed around the chamber130, extending radially from the chamber130to the housing exterior surface120; and a housing bottom portion140located below the chamber130, extending from the chamber130to the turntable engagement surface124.

As depicted inFIG. 4, the housing exterior surface120is substantially rounded with respect to the first rotational axis114. In this manner, the housing112is configured to rotate about the first rotational axis114relative to the machining center102without substantially changing a footprint of the housing112with respect to a work space defined in the machining center102. As a result, when the housing112is installed in the machining center102, the housing112may rotate freely about the first rotational axis114without causing interference between the housing exterior surface120and the machining center102.

With reference toFIG. 3, a piston142is slidably disposed in the chamber130and configured for being driven between an extended position and a retracted position relative to the chamber130. As shown, when the piston142is disposed in the extended position, the piston142is disposed toward the housing top portion132and abuts raised top portion sections144extended into the chamber130from the housing top portion132. Because the piston142is substantially flat when taken from a side view as inFIG. 3and the raised top portion sections144make the chamber130uneven at the housing top portion132, a gap150forms between the housing top portion132and the piston142when the piston142is in the extended position abuts the raised top portion sections144.

At least one spring152is interposed between the piston142and the chamber130. As shown, the at least one spring152is seated on the housing bottom portion140and configured to bias the piston142toward the extended position. An O-ring154disposed circumferentially around the piston142maintains contact with the housing wall portion134as the piston142is actuated between the extended position and the retracted position. In this manner the O-ring154seals a first chamber part160from a second chamber part162, where the gap150is formed in the first chamber part160and the at least one spring152occupies the second chamber part162.

A drawbar164fixed with the piston142includes a drawbar proximal end170and a drawbar distal end172. The drawbar164extends from the piston142and through the first chamber part160, with the drawbar proximal end170connected to the piston142in the chamber130. The drawbar distal end172is spaced from the drawbar proximal end170along a length of the drawbar164and disposed in a bore174defined in the housing top portion132. The bore174extends through the housing top portion132to the housing exterior surface120, and the drawbar164is disposed entirely in the housing112between the chamber130and the bore174.

With continued reference toFIG. 3, the drawbar distal end172is connected to a clamping mechanism180configured for releasably engaging a retention stud182of the workpiece assembly110. Because the piston142is fixed with the drawbar164and configured for being driven between the extended position and the retracted position, the piston142is configured for driving the drawbar164between an extended state and a retracted state which respectively correspond with the extended position and the retracted position of the piston142.

The clamping mechanism180is disposed entirely in the bore174and includes a clamping wall184configured for releasably engaging the retention stud182when actuated from an open position to a locked position. The clamping wall184has a proximal clamping wall portion190that is relatively thin as compared to a distal clamping wall portion192extended from the proximal clamping wall portion190, the distal clamping wall portion192being relatively thick as compared to the proximal clamping wall portion190.

The bore174has a first bore section194that features a relatively wide inner diameter as compared to a second bore section200, which is relatively narrow as compared to the first bore section194. The distal clamping wall portion192occupies the first bore section194when the clamping mechanism180is in the open position, and the distal clamping wall portion192occupies the second bore section200when the clamping mechanism180is in the locked position. As such, when the clamping mechanism180is actuated from the open position to the locked position, the distal clamping wall portion192moves to occupy a relatively narrow section of the bore174. A width of the distal clamping wall portion192in the first bore section194is wider than an inner diameter of the second bore section200such that the proximal clamping wall portion190is enabled to pivot, moving the distal clamping wall portion192radially outward with respect to the first rotational axis114so as to release the workpiece assembly110from the housing112, when the clamping mechanism180is actuated from the locked position to the open position. When the clamping mechanism180is actuated from the open position to the locked position, the distal clamping wall portion192is restricted radially inward by the bore174toward the first rotational axis114such that the clamping mechanism180is closed over the retention stud182and the workpiece assembly110is locked with the housing112.

Because the drawbar distal end172is fixed with the clamping mechanism180and the drawbar164is configured for being driven between the extended state and the retracted state, the drawbar164is configured for driving the clamping mechanism180between the open position and the locked position where the open position and the locked position respectively correspond with the extended state and the retracted state of the drawbar164, and also respectively correspond with the extended position and the retracted position of the piston142. Also, because the piston142is biased toward the extended position, the clamping mechanism180is biased toward the open position.

According to an embodiment of the pneumatic fixture clamp100depicted inFIG. 5, a fluid passage202defined in the housing112is configured for providing fluid to the chamber130by connecting the first chamber part160with a pressure source204(SeeFIG. 2), and alternatively relieving fluid from the chamber130by connecting the first chamber part160with ambient atmosphere. When the fluid passage202connects the chamber130to the pressure source204and the pressure source204is actuated, an increased pressure in the first chamber part160drives the piston142to the retracted position, against the bias imposed on the piston142by the at least one spring152. As a result, the drawbar164is driven toward the retracted state and consequently the clamping mechanism180is driven toward the locked position, locking the workpiece assembly110with the clamping mechanism180. With this construction, taken as a whole, the pneumatic fixture clamp100is biased toward an unlocked configuration with respect to the workpiece assembly110and is pneumatically driven toward a locked configuration with respect to the workpiece assembly110.

The fluid passage202includes a first fluid passage section206and a second fluid passage section210. As shown, the first fluid passage section206extends from the chamber130to a valve212and is entirely defined in the housing112. More specifically, the first fluid passage section206is entirely defined in the housing wall portion134between the chamber130and the valve212, extending in a radial direction of the housing112that is perpendicular to the first rotational axis114. The second fluid passage section210is connected to the valve, extends between two points of the housing exterior surface120, and is entirely defined in the housing112. More specifically, the second fluid passage section210extends from the turntable engagement surface124of the housing112at a point centered on the first rotational axis114, forming an opening220centered on the first rotational axis114at the turntable engagement surface124of the housing112. The second fluid passage section210extends through the housing bottom portion140from the first rotational axis114, and through the housing wall portion134to the valve212. With this construction, the second fluid passage section210is entirely defined in the housing bottom portion140and the housing wall portion134.

The valve212is connected to the fluid passage202between the first fluid passage section206and the second fluid passage section210to selectively bring the first fluid passage section206in fluid communication with the second fluid passage section210. The valve212has an outlet configured for selectively exhausting fluid to the ambient atmosphere. In a first operating position, the valve212brings the chamber130in fluid communication with the pressure source204by bringing the first fluid passage section206in fluid communication with the second fluid passage section210. In a second operating position, the valve212brings the chamber130in fluid communication with the ambient atmosphere by bringing the first fluid passage section206in fluid communication with the ambient atmosphere.

A fitting222is disposed on the housing exterior surface120and defines a passage224that continues the fluid passage202and connects the fluid passage202with a fluid line230configured to supply fluid from the pressure source204to the pneumatic fixture clamp100. As shown, the fluid passage202at the fitting222is defined through the turntable engagement surface124. With continued reference toFIG. 5, the fitting222is disposed on the turntable engagement surface124of the housing112and is centered on the first rotational axis114. Because the fitting222is centered on the first rotational axis114, the fitting222is configured to rotate with the housing112in the machining center102about the first rotational axis114, without the rotation substantially changing a footprint of the fitting222with respect to the housing112or the machining center102.

Notably, a flow path of the fluid includes each of the first chamber part160, the fluid passage202, the pressure source204, the valve212, the fitting222, and the fluid line230. The fluid may be a gas, such as compressed air, and may alternatively be a liquid suitable for selectively introducing and maintaining pressure from the pressure source204in the first chamber part160. As such, the first chamber part160, the fluid passage202, the pressure source204, the valve212, the fitting222, and the fluid line230are each configured to functionally communicate a gas or a liquid with respect to the pneumatic fixture clamp100, in accordance with the physical embodiment of the fluid.

The valve212is mounted on the housing exterior surface120at the housing wall portion134, and occupies a same longitudinal position relative to the housing112along the first rotational axis114as the chamber130. The valve212is configured for remote operation and, in an embodiment of the pneumatic fixture clamp100, the valve212is configured for operation from a machine user interface (not shown). The valve212can be solenoid-actuated valve having a wireless receiver and power source. The wireless receiver can receive wireless signals from an operator, for example, which can control the solenoid to change the operating position of the valve212.

As shown inFIG. 6, the housing exterior surface120is substantially rounded with respect to the first rotational axis114, except for a flat section232on which the valve212is mounted, the flat section232being formed in the housing exterior surface120. The housing exterior surface120at the flat section232is located closer to the first rotational axis114as compared to the housing exterior surface120at a same longitudinal position of the housing112as the flat section232, and because the valve212is mounted on the flat section232, the valve212is located closer to the first rotational axis114than if the valve212were mounted elsewhere on the housing exterior surface120at a same longitudinal position of the housing112as the flat section232.

The valve212is mounted to the flat section232via a valve inner surface234and with this construction, the housing exterior surface120is located further from the rotational axis114than the valve inner surface234in a direction radially outward from the rotational axis114at a position of the valve212along the rotational axis114. Also, a valve outer surface236defining on a side of the valve212opposite the valve inner surface234is located closer to the first rotational axis114than if the valve212were mounted elsewhere on the housing exterior surface120at a same longitudinal section of the housing112. Consequently, a footprint of the valve212taken from a top view of the pneumatic fixture clamp100as shown inFIG. 6is reduced, such that the valve212can rotate with the housing112and to produce a relatively small impact on an overall footprint of the housing112in the machine center102while providing selective communication between the first fluid passage section206and the second fluid passage section210. Notably, while the valve212is depicted with a particular radial position on the housing112with respect to the rotational axis114, the valve212may be located at any radial position on the housing112without departing from the scope of the present disclosure. In further alternative embodiments of the pneumatic fixture clamp100, the valve212could be located elsewhere on or in the housing112for rotation with the housing112.

According to an embodiment of the pneumatic fixture clamp100depicted inFIG. 7, a fluid passage300is defined in the housing112where a first fluid passage section302of the fluid passage300extends from the first chamber part160of the chamber130and directly to a second fluid passage section304, and the second fluid passage section304extends directly from the first fluid passage section302to the fitting222at the turntable engagement surface124of the housing112. The first fluid passage section302and the second fluid passage section304are defined entirely in the housing112, with the first fluid passage section302defined in the housing wall portion134and the second fluid passage section304defined in the housing wall portion134and the housing bottom portion140.

As shown inFIG. 8, the fluid passage300is connected to the fluid line230for fluid communication with a valve310and the pressure source204, the valve310having a similar construction to the valve212shown inFIGS. 5 and 6. With continued reference toFIG. 8, the fluid line230is fixed to the fitting222, disposed external to the housing112, and configured for communicating fluid between the chamber130, the ambient atmosphere, and the pressure source204. The valve310is disposed on the fluid line230, separate from the pneumatic fixture clamp100. The valve310has a first operating position that brings the fluid line230, the fluid passage300, and the chamber130in fluid communication with the pressure source204. In a second operating position, the valve310brings the fluid line230, the fluid passage300, and the chamber130in fluid communication with the ambient atmosphere. In this manner, the piston142is driven toward the retracted position when the valve310is in the first operating position and the pressure source204is actuated, and the piston142is biased toward the extended position by the at least one spring152when the valve310is in the second operating position.

Because the retracted state of the drawbar164and the locked position of the clamping mechanism180correspond with the retracted position of the piston142, the retracted state of the drawbar164and the locked position of the clamping mechanism180also correspond with the first operating position of the valve310. Similarly, because the extended state of the drawbar164and the open position of the clamping mechanism180correspond with the extended state of the piston142, the extended state of the drawbar164and the open position of the clamping mechanism180also correspond with the second operating position of the valve310. By selectively actuating the valve310between the first operating position and the second operating position, a user is able to reconfigure the clamping mechanism180between the locked position and the open position.

With continued reference toFIG. 8, the housing112is mounted on the machining center102, the valve310is mounted on the machining center102and connected to the fluid line230a distance from the housing112, and the fluid line230is directed through the machining center102from the fitting222to the valve310. More specifically the valve310is mounted on a back portion of the machining center102, away from the work space defined in the machining center102for discharging fluid from the fluid line230away from a user and the work space. Because the valve310is located on the machining center102a distance from the machining center102, the turntable104of the machining center102is able to rotate without interference between the valve310and the machining center102. The valve310is configured for remote operation and, in an embodiment, is operated from the machine user interface of the machining center102. For the purpose of selectively connecting the chamber130with the pressure source204, the valve212can be located anywhere on the fluid line230upstream of the204.

In an embodiment, the valve212is mounted on the housing112as depicted inFIG. 6, and the valve310is mounted a distance from the housing112on the machine center102as depicted inFIG. 8, where the valve212and the valve310are disposed in the respective first operating position to bring the pressure source204in fluid communication with the chamber130, such that a user may optionally actuate either the valve212or the valve310into the respective second operating position to bring the chamber130in fluid communication with the ambient atmosphere. In a further embodiment, the valve212is configured for being operated manually such that a user may actuate the valve212while maneuvering the workpiece assembly110, and the valve310is configured for being operated remotely such that a user may actuate the valve310from a remote position with respect to the machine center102.

As shown inFIG. 7, the fitting222is disposed on the housing exterior surface120, defines the passage224, continues the fluid passage300at the second fluid passage section304, and connects the fluid passage300with the fluid line230. At the fitting222, the fluid passage300is defined through the turntable engagement surface124of the housing112and is centered on the first rotational axis114. The fitting222is disposed and centered on the turntable engagement surface124of the housing112, and connects the fluid line230to the housing112. As shown inFIG. 8, the fitting222also directs the fluid line230from the housing112and through the turntable104, away from the work space defined in the machining center102. This allows the turntable104of the machining center102to rotate with the housing112mounted thereon, without interference between the machining center102and the fitting222or the fluid line230.

As shown inFIG. 6, the work engagement surface122includes at least one precision bore240disposed about the first rotational axis114. In the depicted embodiment, the at least one precision bore240includes four precision bores240disposed about the first rotational axis114at 90° intervals such that lines drawn respectively from consecutive precision bores240to the first rotational axis114form right angles, and the precision bores240are disposed at varying distances from the first rotational axis114. The precision bores240are configured for receiving pins (not shown) engaged with the workpiece assembly110, so as to prevent the workpiece assembly110from pivoting about the first rotational axis114relative to the housing112. Notably, while the depicted set of precision bores240includes four precision bores240disposed at 90° intervals about the rotational axis114and at various distances from the rotational axis114, more or fewer precision bores may be employed with alternative patterns of spacing with other precision bores, and alternative patterns of distancing from the first rotational axis114without departing from the scope of the present disclosure.

The work engagement surface122includes at least one threaded hole242respectively configured for receiving a screw (not shown), where the screw is configured to engage the workpiece when the workpiece is being loaded onto the pneumatic fixture clamp100. As depicted, the at least one threaded hole242is four threaded holes respectively located on a line drawn between opposing precision bores240, and the threaded holes are 10-32 United National Fine Threads (UNF) threaded holes configured for respectively receiving 10-32 UNF screws. Notably, the at least one threaded hole242may employ more or fewer threaded holes, may be disposed about the work engagement surface122without being located on a line drawn between two opposing precision bores240, and/or may have a size other than 10-32 UNF without departing from the scope of the present disclosure.

According to an aspect of the present disclosure, a method of operating the pneumatic fixture clamp100includes releasing the workpiece assembly110from the pneumatic fixture clamp100by actuating the valve212from the first operating position, bringing the chamber130defined by a housing112in fluid communication with the pressure source204, to the second operating position, where the chamber130is in fluid communication with the ambient atmosphere so as to release fluid from the chamber130through the fluid passage202defined in the housing112. The fluid passage202includes the first fluid passage section206extending from the chamber130and the second fluid passage section210section extending from a housing exterior surface120, such that actuating the valve212from the first operating position to the second operating position releases fluid through at least the first fluid passage section206.

The method also includes driving a piston142slidably disposed in the chamber130from the retracted position to the extended position, driving the drawbar164from the retracted state corresponding with the retracted position of the piston142to the extended state corresponding with the extended position of the piston142, and unlocking the clamping mechanism180from the workpiece assembly110, the clamping mechanism180being connected to the drawbar distal end172, the drawbar164being connected to the piston142at a drawbar proximal end170. In an embodiment, the method further includes locking the workpiece assembly110with the pneumatic fixture clamp100by actuating the valve212from the second operating position to the first operating position, and actuating the pressure source204so as to introduce fluid first through the second fluid passage section210, then the first fluid passage section206. The method further includes driving the piston142from the extended position to the retracted position, driving the drawbar164from the extended state to the retracted state, and locking the clamping mechanism180to the workpiece assembly110.

Notably, while the depicted embodiments of the pneumatic fixture clamp100feature the first chamber part160connected to the fluid passage202where the second chamber part162houses the at least one spring152, the first chamber part160and the second chamber part162may be functionally switched such that the first chamber part160houses the at least one spring152and the second chamber part162is connected to the fluid passage202and configured for accepting fluid so as to drive the piston142, without departing from the scope of the present disclosure.