Patent Application
20080060740
A clamping head positioner 115 is coupled to the work surface 105 by a support 110. It is preferable that the support 110 be a rigid structure that is capable of maintaining a fixed position for the clamping head positioner 115 with respect to the work surface 105 during operation. It is desirable to minimize oscillation or displacement of the clamping head positioner 115 during operation.
In an alternative embodiment, the clamping head positioner 115 and the work surface 105 are not directly coupled, but are otherwise restrained so that clamping head positioner 115 and work surface 105 maintain a fixed separation during operation. For example the work surface 105 and/or clamping head positioner 115 may supported by or mounted on a floor or wall.
The clamping head positioner 115 includes an actuator that provides vertical displacement to the clamping head 120. Examples of actuators that may be used are pneumatic cylinders and solenoids. The clamping head 120 includes a pair of jaws 125. The opening and closing of the jaws 125 may be synchronized with the vertical displacement of the clamping head 120.
The clamping head positioner 115 and the clamping head 120 are coupled to a controller 135. The controller 135 controls the timing of the vertical displacement of the clamping head 120 and may also control the timing of the opening and closing of the jaws 125.
For example, when a pneumatic cylinder is used as the actuator for providing vertical displacement of the clamping head 120, the controller may be used to control the gas flow to the pneumatic cylinder. On/off solenoid valves may be used, in which case the vertical displacement rate of the clamping head 120 may be adjusted by changing the working gas pressure. Alternatively, the vertical displacement rate of the clamping head 120 may be adjusted by using a proportional valve to meter gas from a constant pressure gas source.
Clamping head positioner 115 may include a sensor for determining the position of the clamping head 120 with respect to the clamping head positioner 115. For example a pneumatic cylinder with an integrated magnetic sensor may be used to provide the vertical displacement. Since the clamping head positioner 115 is essentially fixed with respect to the work surface 105, the displacement between the clamping head positioner 115 and the clamping head 120 may be used to determine the displacement between the jaws 125 and the work surface 105.
The clamping head 120 may include a light source for illuminating a portion of a workpiece to aid in the alignment of the workpiece with respect to the jaws 125. The light source may be a solid-state laser.
The maximum value for the vertical separation (h) between the jaws 125 and the work surface 105 is preferably a value that is sufficient to allow for the unhindered positioning of wetsuit panels or a partially assembled wetsuit beneath the jaws 125. The minimum value for the jaw separation (s) is that required to allow the jaws to provide sufficient compression to mated edges of wetsuit panels that are being bonded.
The separation (h) may be established through force limit or by displacement limit. The force limit may be established by a preset limit on the force used to drive the vertical displacement of the clamping head, or it may be determined by a feed back loop. When force feedback is used, the load against the jaws 125 is sensed and the downward vertical displacement of the jaws 125 is halted when the force between the jaws 125 and the wetsuit panels reaches a predetermined value. Force feedback allows the vertical separation (h) to vary from cycle to cycle, and is useful when the thickness of the material beneath the jaws 125 varies over a large range.
The vertical separation (h) may be established by using a mechanical stop to limit the vertical displacement of the clamping head 120. For example, a pneumatic cylinder may be cycled between its inherent limits. A displacement limited separation (h) is not easily modified on a per cycle basis, but may provide faster cycle times since a feedback loop is not required. The vertical separation (h) may be adjusted by changing the position of the clamping head positioner 115 with respect to the support 110.
The jaws 125 are typically maintained in an open position until the minimum vertical separation (h) is reached during a downstroke of the clamping head 120, or contact is established with the workpiece. When a displacement limit is used, closure of the jaws 125 is initiated after jaws 125 have reached the displacement limit. A short delay may be inserted between the arrival at the lowest position and the closure of the jaws to allow for damping of oscillations in the system.
Similar to the displacement of the clamping head 120, the closure of the jaws 125 may be force limited or displacement limited. The minimum jaw separation (s) may be determined by feedback from a force sensor, setting the maximum force used to close the jaws 125 or it may be determined by a mechanical stop. Once the jaws 125 are closed, a dwell time may be observed prior to opening of the jaws 125 and the retraction of the clamping head 120.
In one embodiment detection of an occurrence of signal by the trigger sensor 130 may be used to cause the controller 135 to initiate a single clamping cycle. In an alternative embodiment the controller 135 may repeat the clamping cycle as long as the signal is detected by the trigger sensor 130. Logically speaking, the operation may be either edge-triggered or level-triggered.
The trigger sensor 130 may be a foot switch, motion detector, optical scanner, acoustic recognition device, or other sensing device that is capable of interpreting an action on the part of the operator. An operator's voice or movement of an operator's head or eyes may be used as signal for the trigger sensor 130.
In order to maximize the operational speed and precision of the dynamic jaw module 300 it is desirable to minimize the mass of moving parts, particularly those parts that are subject to rapid acceleration. Double-acting air cylinders are preferable to single-acting air cylinders due to the absence of return spring resistance on the downstroke and a greater available force on the return stroke.
Since the tips of the jaws 405 travel in an arc, a long stroke or a thin panel may result in an unacceptably large force component normal to the work surface. The normal force component may be reduced by increasing the distance between the pivot shaft and the jaw tips.
The jaws 425 have a relief 435 on the inner clamping surfaces. A finite amount of compression of the wetsuit panels is required to develop the friction that allows the jaws 425 to compress the mated panel edges together. Most of the compression is obtained at the heel 440, while the relief 435 reduces vertical compression of the panel edges that may degrade the seam. The relief 435 allows the jaws 425 to be operated closer to the seam with a shorter stroke.
At step 505 a trigger signal from an operator is detected. The trigger signal may be conditioned by a sensor such as trigger sensor 130 of
At step 510 a downstroke of the clamping head 120 is initiated. Initiation of the downstroke may be accomplished by operation of one or more pneumatic valves or the switching of one or more solenoid actuators.
At step 515 the clamping head position is detected. The clamping head position may be monitored continuously during the downstroke or the arrival at a specific position may be detected. The position being detected may be correlated with a reactive force produced by contact with a workpiece.
At step 520 the jaws 125 are closed. The closure of the jaws may be displacement limited or force limited. For systems in which the clamping head downstroke is accomplished at high speed, jaw closure may delayed by the controller after the detection of the clamping head position to allow a short period of time for damping of mechanical oscillations and relaxation of the workpiece that is being compressed.
At step 525 the jaws 125 are held in a closed position for a preset dwell time to allow intimate contact to be established between the mated edges of the wetsuit panels that are being bonded. A mechanical system will typically have an inherent delay; however, the inherent delay in a high-speed machine may be too short to allow for optimum bonding, thus a programmed dwell time may be used to enhance bonding.
At step 530 the jaws are opened and at step 535 the clamping head 120 is returned to its starting position. In contrast to the downstroke and jaw closure operations, it is preferred that steps 530 and 535 are performed without an intermediate delay. In order to provide optimum performance, it is desirable to minimize inherent delays in the system and insert programmed delays as necessary.
At step 610 the prepared edges of the panels are aligned and brought into contact. At step 615 the mated panel edges are aligned between jaws 125 and the work surface 105. At step 620 a trigger signal is sent by the operator to initiate an automated clamp cycle similar to that shown in
At step 635 steps 620-630 are repeated until the length of the mated panel edges has been compressed by the jaws 125. It is to be understood that the repetition of step 620 may be either the transmission of a new signal (edge trigger) or the continuation of the initial signal (level trigger). Edge triggers and level triggers may be alternately used during the fabrication of a single wetsuit.
While the invention has been described in detail with reference to preferred embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention.
