Patent Application
20050019120
1. Field of the Invention
The invention pertains to the field of worm gears. More particularly, the invention pertains to a worm gear having a thread pitch.
2. Description of Related Art
It is known to form a gear, wherein the outer circumference (i.e., all 360° ) of the gear is covered with a tooth-like structure. Such gears commonly are used inside a wide variety of mechanical devices, such as, for example, gear-boxes for valves, clocks, watches, compasses, motors, etc. The gear can be a worm gear, which possesses a specific pitch, with all worms associated with the gear based on that pitch (i.e., with the pitch covering the 360° circumference of the gear). Pitch is defined as the distance from center to center of any two adjacent teeth of a gear, measured on the pitch line. This type of pitch is also known as circular pitch.
All known worms and worm gears are based on a 360° formation, or have tooth-like structures distributed circumferentially upon the outside surface. For example, the formation may have 3.7836 threads per inch.
The formation of gears is different than tapping an inner thread. In fact, the formation of gears generally involves moving a gear blank for forming teeth thereon by a moving hob. The above technique is well known in the art. A list of publications detailing such technique is as follows, and the complete disclosures of each of the references on the list are hereby incorporated herein by reference in their entireties: (1) Pictorial Handbook of Technical Devices, section V, pages 404-405. (2) Encyclopedia of Modern Technology (a new companion volume thereto), Vol.2, pages 166-169. (3) Machinery's Handbook (1957), pages 774-779, 788-789, and 800-801.
One characteristic of the gearing-forming techniques of the prior art is that the gear blanks are required to move, in order for a hob to perform the tooth-forming operations. This requirement puts a demand upon the system characteristics of a gear-forming system, in that stringent system requirements are imposed. For example, the accuracy of the system needs to be such that proper tooth structures are achieved.
Taps also are known in the art of mechanical engineering. According to various characteristics, taps include, for example a straight flute tap, spiral point tap, spiral flute tap, and pipe tap. It generally is well known to use a tap for forming internal or female threads within an article, although it is not known in the art to use a tap for gear manufacturing.
Thread tapping machines are well-known in the art as well. These machines are used, for example, to tap or form female (i.e., internal) threads in articles, such as, for example, rods, fasteners, nuts and various other mechanical parts. In reference (3) of the list above, Machinery's Handbook (1957), pages 990-991 and 994-995, some types of prior art tapping are shown.
As can be seen, a thread pitch and a worm pitch are two different things from two different systems. In other words, a 360° worm pitch and 360° thread pitch are not known to properly engage or match. Therefore, a suitable device or method that can provide a thread pitch on a worm gear would achieve an improved means for forming a gear including a partial worm gear. Such improved worm gears could be widely applied in the mechanical arts, such as, for example, in gear-boxes for valves.
A method of using a tap for forming a gear is provided. The method uses a tap, which is coupled to an actuator for supplying an actuating force on the tap. The tap, in turn, forms thread on a gear blank.
A method of using a tap for forming a partial-turn gear is provided. The method uses a tap, which is coupled to an actuator for supplying an actuating force on the tap. The tap, in turn, forms thread on a partial-turn gear blank.
A method of using a tap for forming a plurality of partial-turn gears is provided. The method uses a tap, which is coupled to an actuator for supplying an actuating force on the tap. A plurality of gear blanks passively receives the actuated tap, thereby forming threads thereon.
Accordingly, a method for forming gear threads on a gear blank is provided. The method includes: providing a tap coupled to and acted upon by an actuator; providing a plurality of blanks, wherein each blank has a surface for threading and each blank is free from actuation, other than active forces exerted by the tap; placing the blank surfaces facing each other for engagement with the tap; actuating the tap upon the blank surfaces; and forming threads on the blank surfaces.
A system for forming gears using a tap is provided. The system includes: a tap driver; a tap coupled to and driven by the tap driver; and a plurality of gear blanks, wherein each blank has a surface disposed to be engagable by the tap for threading thereon; whereby gears are formed free from a hob and active actuation on the gear blanks.
The present invention involves the formation of less than 360° turn gears, such as for use in quarter-turn gear boxes. The less than 360° segment gear may be used for meshing with a worm, wherein the worm has a threaded pitch, formed by means of using a tap.
As can be appreciated, a gear having its circumference (all 360° ) covered with tooth-like structures is known. In some cases, a less than 360° turn gear is required or desired. In these cases, it may not be necessary to actively actuate the gear blanks under processing. That is to say, to put threads on a partial-turn gear, such as a quarter-turn worm gear, no actuator for the blanks is needed. In other words, a partial-turn gear blank passively receives the action of a tap, which is coupled to an actuator, while the blanks themselves do not receive actuating actions, other than from the tap.
Partial-turn gears have extensive use in industry. By way of an example, there is a big market for x° turn gears (i.e., wherein “x” is equal to a number less than 360), which may be used in association with such devices as valves, for example. One of the characteristics of the x° turn gears is that a less than 3600 turn is required. Generally, quarter-turn gears are x° turn gears that require about a 90° turn. Because of this characteristic, a tap, which is known to be used for threading such members as an article with a hollow blank element, can be used to prepare the x° turn gears. Preferably, more than one x° turn gear is used for this process.
Tap 1 having protrusions (not shown) thereon is actuated by an actuator 3, which may give tap 1 a turning force. It is noted that the actuating mechanism 3 and tap 1 may be similar to prior art devices for forming female threading. However, the present invention teaches using a tap for forming a gear, such as, for example, a quarter-turn worm gear. Further, the whole structure of the partial-turn blank may reside within a holding member 4. Holding member 4 facilitate a desired turning action, caused by the actuating force of the tap. Thereby, the partial-turn blank surface can be evenly threaded. There is no actuating force exerted by holding member 4 upon any partial-turn blank.
As can be appreciated, the present invention forgoes the elaborate process of gear forming using a hob acting upon gear blanks, which requires an actuator acting thereon. Because the present invention teaches forming partial-turn gears, the force exerted by the tap is sufficient for threading on the blank surfaces, which does not have the 360 degree characteristics. Therefore, the blanks can be positioned passively to receive the tap. A holding member may be required to facilitate a smooth turning of the blanks.
It should be noted that the present invention also contemplates the manufacture of full 360 degree turning gears using a tap. However, the preferred embodiment is a method for forming partial-turn worm gears.
The present invention teaches cutting a gear with a thread pitch using a thread rod or tap. The thread rod or tap are preferably of the widely available and the inexpensive type. The present invention teaches cutting teeth on a gear in a novel and special way, using the threading mechanism of a tap, which is generally used for internal threading purposes.
Referring to
As a special example, the following are more specific steps in relation to the method or flowchart of
The present invention teaches a method using a tap instead of using a hob for forming gear teeth. The method forgoes the usage of extensive and expensive machinery, including means for actively moving the gear blanks for tooth cutting by a hob. The method simply uses a tap, as shown in the above process. Thereby it is less expensive in making gears having less than 360 degree turns. The resultant gear may be used for interacting with worms.
In addition, referring again to
It is again noted that generally thread pitch is distinct from gear pitch. However, the present invention teaches a method for forming gear pitch using a tap which is generally only known to be used for thread pitch forming.
The following figures,
Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.
