Patent Application
20070273059
A better understanding of the exemplary embodiments of the present invention (including alternatives and/or variations thereof) may be obtained with reference to the detailed description of the exemplary embodiments along with the following drawings, in which:
The drawings are not necessarily to scale and are sometimes illustrated by phantom lines, diagrammatic representations and fragmentary views. In certain instances, details that are not necessary for an understanding of the embodiments or that render other details difficult to perceive may have been omitted.
The molding system 10 includes a frame 20. The stationary platen 12 is operatively mounted to the frame 20. Guide rails 18 are supported by the frame 20, and the movable platen 14 is mounted so as to be slidable along the guide rails 18 toward and away from the stationary platen 12. Tie bars 16 extend from the stationary platen 12 toward the movable platen 14, and the movable platen 14 is slidably engagable with the tie bars 16. The movable platen 14 has a mold-bearing surface 15 to which a mold half (not depicted) may be removably mounted thereto. Similarly, the stationary platen 12 has a mold-bearing face (hidden in this view) to which another mold half may be fixedly mounted. A clamping actuator 22 is used to apply a clamp-up force to the mold halves (via the tie bars 16) after the MSP actuator 100 has stroked the platens 12, 14 so that the mold halves may become closed against each other. An injection unit (not depicted in this view) is used to inject a molding material into a cavity defined by the mold halves to form a molded article. Once the molded article is formed and solidified in the mold cavity, the MSP actuator 100 is used to: (i) apply a mold-break force to the platens 12, 14 so as to break open the mold halves, and then (ii) stroke the platens 12, 14 apart after which the molded article may be removed from the mold halves. Then, the mold may be closed for the next cycle of the molding system.
Preferably, two MSP actuators 100 are used such as: (i) a first actuator is located above the stationary platen 12, and (ii) a second actuator is located below the stationary platen 12 (at opposite corners of the platens) so as to: (i) improve stoke movement of the platens 12, 14 and (ii) maintain the mold-bearing surfaces substantially parallel while the platens 12, 14 are stroked. It will be appreciated that one, two or more MSP actuators may be used as may be needed depending on the requirements imposed by a molding system.
In operation, the stator 112 and the rotor 114 are energized so that the rotor 114 rotates the ball nut 116. Once the ball nut 116 rotates, the ball nut 116: (i) rotatably travels along the ball screw 118 and (ii) urges the ball screw 118 to linearly stroke.
Preferably, the MB actuator 104 includes components that are arranged to actuatably impart a mold-break force 132 onto a platen (either the stationary platen 12 or the movable platen 14) so that the mold-break force 132 may be transmitted to the mold. Preferably, a distal end of the in-line housing 106 is sealed with an end cap 120. The supports 107 are used to: (i) maintain the end cap 120 in place, and/or (ii) improve the structural integrity of the in-line-housing 106, which is depicted as a cylinder.
A guide bushing 134 is linked or attached to the end of the ball screw 118. The guide bushing 134 is equipped with a vent 135 that allows air to flow freely between: (i) a space defined between the piston 122 and the guide bushing 134, and (ii) another space defined between the electrical motor 110 and the guide bushing 134. According to a variant, a one-way check valve (not depicted) is embedded in the guide bushing 134 and the vent 135 is not used, and this arrangement allows some air pressure to accumulate and act as a bumper to prevent the guide bushing 134 from striking a piston 122 with too much force.
The piston 122 is slidably mountable within the in-line housing 106, and slidable between the end cap 120 and the ball screw 118. The piston 122 is abuttable against the distal end of the ball screw 118. The piston 122 may be either: (i) attached to the end of the ball screw 118, or (ii) detached from the ball screw 118. When the mold-break force 132 is not required, the piston 122 is not used and it preferably remains positioned in the end of the in-line housing 106.
Located at the end of the in-line housing 106 near the end cap 120 (between the piston 122 and the end cap 120), there is a hydraulic chamber 130 (hereafter referred to as “the chamber 130”) to which a pressurized fluid 128 is receivable therein. The port 126 is used to communicate, from a valve (not depicted), pressurized hydraulic fluid 128 with the chamber 130. The port 126 is used to allow the pressurized hydraulic fluid 128 to flow in or out of the in-line housing 106 (preferably at low pressure). Preferably, the port 126 is contained in the end cap 120. A seal 124 is used to: (i) seal the piston 122 against the in-line housing 106 so as to prevent leakage of the hydraulic fluid, but (ii) permit the piston 122 to slide along the in-line housing 106. Alternatively, another port (not depicted) is provided to permit the hydraulic fluid 128 to flow out of the in-line housing 106.
A decision to stop the flow of pressurized fluid 128 to the chamber 130 may be based on: (i) a position of the mold halves, (ii) a timer indication, and/or (iii) an amount of pressure decay (of the pressurized fluid 128) after the mold halves begin to open (in any combination or permutation thereof). As the mold halves spread apart, the ball screw 118 escapes away from the piston 122.
When the mold halves are closed against each other, the end of the ball screw 118 pushes the piston 122 back towards the cap 118, exhausting the fluid 128 in the chamber 130. The floating piston 122 operates in the portion of the in-line housing 106 which is defined by a closed height of the mold. The floating piston 122 is self-adjusting for mold-height variation.
According to a variant, air pressure is generated between the piston 122 and the guide bushing 134, which could be used to push the piston 122 back or reduce the impact load between the ball screw 118 and the piston 122 during closure of the mold.
According to a variant, the guide bushing 134 or the piston 122 is equipped with a bumper (not depicted) made of a flexible material or a separate spring-loaded assembly to cushion impacts.
The description of the exemplary embodiments provides examples of the present invention, and these examples do not limit the scope of the present invention. It is understood that the scope of the present invention is limited by the claims. The concepts described above may be adapted for specific conditions and/or functions, and may be further extended to a variety of other applications that are within the scope of the present invention. Having thus described the exemplary embodiments, it will be apparent that modifications and enhancements are possible without departing from the concepts as described. Therefore, what is to be protected by way of letters patent are limited only by the scope of the following claims:
