1. Field of the Invention
The present invention relates generally to a crank, and more particularly to an adjustable crank of swinging mechanism, which is particularly adapted for swinging mechanism such as employed in oscillating electric fans or heaters.
2. Description of the Prior Art
Conventional oscillating electric fans available in the market are commonly controlled by an unadjustable swinging mechanism that makes the fan swing at an unadjustable angle range. A user can only choose between a fixed mode (no swing) and a swinging mode with a predefined swinging-angle. Such functions are hard to suit the current environment and meet a user""s requirements. U.S. Pat. No. 5,639,213 is an example of such designs, which employs a commonly used crank and rocker mechanism in such an oscillating fan. U.S. Pat. No. 5,720,594 is another example that discloses a crank and slotopening mechanism for a fan oscillating in two axes.
In order to overcome such weakness, many improved schemes have been developed. Among them, some use a crank with changeable length, which leads the swinging-angle adjustable. U.S. Pat. Nos. 3,977,260, 5,217,417 and 5,931,056 are examples of prior patents that disclose such types of fans and also various crank arrangements used for swinging such fans. Unfortunately, the structures of these schemes are so complex that they are hardly adopted and applied widely. As disclosed in China Pat. No. 95240392, a crankpin of the crank can be moved in a slot resulting in corresponding change of the crank length. But such a crank based on above scheme is not convenient for performing swingiong-angle adjusting, and its structure is not simple. Furthermore, even more complex structures may be seen in some other schemes.
According to the present invention, a novel adjustable crank is provided to solve the problemes mentioned above. Wherein a simple eccentric mechanism is used to change the crank length, an ingenious coupling means is used to self-fix the crank length, an adjusting means is used to conveniently adjust the crank length, furthermore, several additional means are used for making adjustment to the crank length more conveniently.
The adjustable crank according to the present invention comprises a first eccentric disk, a second eccentric disk, a coupling means and an adjusting means. The first disk is provided with a recess having an inner cylindrical surface and an integrally formed crankpin, which is eccentric with respect to the inner cylindrical surface. The second disk is provided with an outer cylindrical surface and a rotation means for the second disk be turned to rotate about a center axis, which is eccentric with respect to the outer cylindrical surface. The second disk is rotatablely inserted in the first disk, and so the inner cylindrical surface and the outer cylindrical surface are engaged each other. The coupling means is disposed between the first and second disks for coupling both of them with predetermined coupling torque. The predetermined coupling torque is large enough to ensure that the relative positions of the first and second disks can be maintained during operation so that power actuating the fan head to swing can be transmitted through the crank. The adjusting means is positioned on the end of the crankpin for manually turning the first disk to rotate relative to the second disk with adjusting torque, which is greater than the coupling torque. Thereby the crank length is adjustable and can be self-fixed after being adjusted. The crank length can be adjusted continuously from zero to the maximum value; correspondingly the swinging-angle of a fan can be adjusted from 0 to a maximum of 120 degrees.
The second disk might provided with a axial mounting hole or with a spindle and a gear, the mounting hole or the spindle and the gear are coaxially disposed with the center axis. Similar to conventional unadjustable cranks the mounting hole is fixedly mounted on an output shaft of an actuating device and actuated to rotate by the output shaft, or the spindle is rotatablely inserted in a locating hole and the gear is actuated to rotate by a pinion of the actuating device. The crankpin is articulated with one end of a connecting rod of a crank and rocker mechanism or slidablely inserted in a slotopening of a crank and slotopening mechanism.
One type of the coupling means is configured such that a pair of annular engaging zones respectively positioned on the first and second disks are forced into coupling together by predetermined elastic force resulted from elastic distortion of at least one of said disks. But then said disks can be forced to rotate relatively by said adjusting means. Said annular engaging zones may be inner cylindrical surface with outer cylindrical surface or annular groove with annular bulge.
Another type of the coupling means comprises a plurality of concaves and at least one convex meshing with the concaves. The concaves and convex are respectively formed on the engaging surfaces of the first disk and second disks. The concaves and the convex can be forced to slip across each other due to elastic deforming of at least one of said disks by said adjusting means, and sound signals and touch signals will be generated at the same time.
Another type of the coupling means comprises a spring means positioned in an annular chamber formed on the engaging surfaces. The spring means can be turned to rotate relative to at least one of said disks and exerts predetermined pressure force on the same disk to couple it with frictional force. Said spring means is selected from the group consisting of metallic round split ring, metallic polygon split ring, elastomeric O-ring, and elastomeric strip, etc. Said annular chamber may be a combination of two annular grooves, one is formed on the first disk and the other on the second disk. Said spring means is partially positioned in one of said grooves and partially positioned in other one so that the axial relative movement of the first and second disks is further limited.
Another type of the coupling means comprises a spring means and at least one steel ball located in a radial hole formed on the second disk, the steel ball is biased to abut against the first disk by predetermined force actuated by the spring means. Furthermore, the first disk can be shaped to include a plurality of concaves or axial grooves formed on the inner cylindrical surface, the steel ball is biased to abut against the concaves or axial grooves. While adjusting crank length, the concaves or axial grooves can be forced to slip across the steel ball, and sound signals and touch signals will be generated at the same time, hereby such coupling means is accompanied by signaling function.
The adjusting means comprises a rotary knob, one end of the rotary knob has an axial hole securely connected with the end of the crankpin; the other end has a handwheel extended out of the through hole formed on the rear housing of the fan motor, so that adjusting torque is directly applied to the handwheel with hand. The handwheel may be concentrical with the crankpin, but preferably is concentrical with the inner cylindrical surface of the first disk.
Alternatively, the adjusting means is configured such that the end of the crankpin being shaped like a screw head, such as slotted head, cross recess head, hex head or square head. Thus, the adjusting torque can be manually applied to the crankpin via a universal screwdriver or other tools.
According to the present invention a signaling means is further comprised for generating sound signal and touch signal during the crank length adjusting process. One type of the signaling means comprises a plurality of axial grooves and at least one axial ridge meshing with said grooves. The grooves and the ridge are respectively formed on the engaging surfaces of the disks. While adjusting cxrank length, said grooves and ridge can be forced to slip across each other due to elastic distortion of at least one of the disks, sound signal and touch signal will be generated at the same time.
According to the present invention a circumferential limiting measns is further comprised, by which the relative rotation of the first and second disks is delimited at two ultimate positions. One of the ultimate positions corresponds to the maximum crank length, and the other one corresponds to the minimum crank length. So the first and second disks can only be to-and-fro turned relatively between these two ultimate positions, one turning direction corresponds to increasing the crank length and the other turning direction corresponds to decreasing the crank length.
One type of the circumferential limiting means includes two axial projecting elements, which are respectively formed on the first and second disks and blocked each other at two ultimate positions. Another type of the circumferential limiting means includes an arc shape groove and an axial projecting element extending into the arc groove, the arc groove and the projecting element are respectively formed on the first and second disks and blocked each other at two ultimate positions.
According to the present invention an axial limiting means is further comprised to limit axial relative movement of the disks. Said limiting means includes a pair of annular shoulders adjacent each other formed respectively on said engaging surfaces. In an alternative way, said limiting means includes an annular bulge and an annular groove formed respectively on said engaging surfaces and meshed each other.
The first disk, second disk and rotary knob as described above can be made of metal or plastic material, but preferably are molded from plastic.
When adjusting crank length, user only need to turn the rotary knob to change the crank length and then the crank length is self-fixed at the desired value by the coupling means. All appearance, the adjustable crank according to the present invention therefore has the advantages of being especially simple in structure, being significantly convenient and cost effective in manufacture, being very easy to adjust during operation and being reliable in running.
Accordingly, it is a principal object of the present invention to provide an adjustable crank, which is especially simple in structure and easy to adjust the crank length.
It is a further object of the present invention to provide a coupling means, which can be used to fix the crank length automatically after the crank length being adjusted.
It is a further object of the present invention to provide an adjusting means, which can be used to adjust the crank length conveniently.
It is an additional object of the present invention to provide a signaling means, which can be used to adjust the crank length efficiently.
It is an additional object of the present invention to provide a circumferential limiting means, which can be used much more conveniently to adjust the crank length.
Further object and advantage is to provide an adjustable crank, which can be simply used to replacing the constant length crank of the existing oscillating fans.
Other objects and advantages will become apparent from a consideration of the ensuing drawings and description.