BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a respective view of a motion mechanism in accordance with the invention for achieving both horizontal and vertical movement.
FIG. 2 is a perspective view of a machining station utilizing the motion mechanism of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Shown in FIG. 1 is a motion mechanism for achieving both horizontal movement in the Y direction and vertical movement in the Z direction. Motion mechanism 10 includes two linear actuator assemblies 12, 14 having carriage assemblies 16, 18 that are moveable along parallel lines (along the Y-axis) in either the same or opposite directions. Slidably supported on carriages 16, 18 is a head 20 for carrying a tool 22 (such as a friction stir welding tool) or workpiece. A first slide assembly 24 comprises a first slide member 26 (a C-shaped guide or track) that is linearly moveable along a second slide member 28 (which in the illustrated embodiment is a rail that slides along a channel defined in the C-shaped first slide member). First slide member 26 is affixed to carriage assembly 16 and second slide member 28 is affixed to a first side 29 of head 20. Slide assembly 24 is oriented to achieve linear motion of head 20 along a line that is at a first acute angle with respect to the parallel lines along which carriages 16, 18 are moveable (along the Y-axis in the illustrated embodiment). A second slide assembly 30 comprises a third slide member 32 that is linearly moveable along a fourth slide member 34. Third slide member 32 is affixed to carriage 18. Fourth slide member 34 is affixed to a second side of head 20 opposite first side 29. In the illustrated embodiment, slide member 32 is a C-shaped member defining a channel or slot along which member 34 slides. Second slide assembly 30 is oriented to achieve linear movement of head 20 along a line that is at a second acute angle which respect to the parallel lines along which carriages 16, 20 are moveable. The second acute angle is of equal magnitude to the first acute angle, but has a slope that is opposite to the slope of the first acute angle (i.e., with respect to the positive direction of the horizontal X-axis, the first angle is negative or has a negative slope, and the second angle is positive or has a positive slope of equal magnitude to the first angle).
As used herein, an acute angle is an angle between 0 degrees and 90 degrees. More typically, for the envisioned applications, the angle is between 0 degrees and 45 degrees (wherein the horizontal to vertical travel ratio is about 1:1). Typically, the acute angle has a horizontal to vertical travel ratio of from about 1:1 to about 10:1, and more typically from about 2:1 to about 5:1.
In the illustrated embodiment, linear actuator assemblies 12, 14 comprise side guide rails 40, 42, an end plate 44, coupling 46, electric motor 48, and threaded rod or lead screw 50 coupled to an output shaft of motor 48. A nut member 52 is treaded onto lead screw 50 and linear bearings support carriages 16, 18. Guide rails 40, 42 are designed to interlock with nut member 52 to keep it from rotating. When lead screw 50 is rotated, nut member 52 and supported carriages 16, 18 move linearly along the longitudinal axis of lead screw 50. Alternatively, linear actuator assemblies may comprise hydraulic, pneumatic, magnetic, and other types of mechanisms capable of achieving linear motion of carriages 16, 18.
As shown in FIG. 2, a machining station 60 in accordance with another aspect of this invention comprises a table 62 having a top 64 supported above a base 66 by legs 68. Affixed to tabletop 64 is at least one linear actuator assembly 12, which may be identical to linear actuator 12 shown in FIG. 1. Each of linear actuator assemblies 12 includes a carriage 70 that is linearly moveable in the longitudinal direction of linear actuator assemblies 12, and which are capable of supporting an object, such as a workpiece. Supported on stanchions 72 is a motion mechanism 10 as shown in FIG. 1. Linear actuator assemblies 12 allow movement of a workpiece supported on carriage 70 along the horizontal X-axis, while motion mechanism 10 facilitates movement of a tool along the perpendicular horizontal Y-axis and the vertical Z-axis.
As can be best understood with reference to FIG. 1, when carriages 16, 18 are both moved in the same direction at the same rate of speed, there can be no relative movement of slide members 28, 34 with respect to slide members 26, 32. As a result, tool 22 is moved only along the horizontal Y-axis. However, when carriage 16 is moved in the positive Y-direction and carriage 18 is moved at the same rate of speed in the negative Y-direction, there can be no movement of head 20 or tool 22 along the Y-axis. Instead, members 28 and 34 slide upwardly with respect to carriages 16 and 18, respectively, causing head 20 and tool 22 to move vertically upward along the Z-axis, for the orientation shown in FIG. 1 (it being understood that this orientation is upside down with respect to a more typical orientation shown in FIG. 2). Movement of carriages 16 and 18 at different rates of speed can achieve a combination of both horizontal and vertical movement simultaneously. In the illustrated embodiments, tool 22 is a friction stir welding tool rotated by an electric motor 76.
The motion mechanism 10 and machining station 60 of this invention are relatively simpler, lighter in weight, smaller, and less expensive than conventional serial and/or parallel motion mechanisms for achieving a comparable result in which short travel distances and high forces are required in the vertical direction. In addition, the apparatuses of this invention have the advantage of utilizing standard actuators that can be identical. For example, linear actuator assemblies 12, 14 can be identical, thereby reducing spare parts inventories. Further, with the mechanisms of this invention, two actuators share the vertical load, allowing lower cost linear bearings and longer component life. The acute angle between the directions of movement of slide members 24, 28 with respect to the horizontal linear movement of carriage 16 determines the horizontal force to vertical force relationship. Small angles allow a high vertical force to be generated using a relatively lower force in the lead screws.
It will be understood by those who practice the invention and those skilled in the art that various modifications and improvements may be made to the invention without departing from the spirit of the disclosed concept. The scope of protection afforded is to be determined by the claims and by the breadth of interpretation allowed by law.
Patent Application
20080087128
