The present invention relates generally to the field of box end ratchet wrenches and ratchet drive wrenches. More specifically, it relates to a box end ratchet wrench and/or a ratchet drive wrench with a multi-pawl assembly that facilitates a reduced ratcheting arc of 5 degrees, 2.5 degrees, 1.75 degrees, or lower.
A ratchet wrench is a type of wrench having at least one end that surrounds a nut or the head of a bolt. The wrench provides a mechanical advantage by applying torque to turn bolts, nuts or other items designed to interface with a wrench. The ratcheting mechanism allows the nut or bolt to be tightened or loosened with a reciprocating motion of the wrench, without requiring that the wrench be removed, refitted or repositioned after each turn.
A ratchet wrench includes ratchet and pawl components known in the mechanical arts to control and secure movement. Ratchets consist of a ratchet wheel, or gear wheel, and may include a spring assembly which applies pressure to a pivoting spring loaded finger called a pawl that engages the teeth. Either the teeth, or the pawl, are slanted at an angle, so that when the teeth are moving in one direction, the pawl slides up and over each tooth in turn, with the spring forcing it back in place with a “click” into the depression before the next tooth. When the teeth are moving in the other direction, the angle of the pawl causes it to catch against a tooth and stop further motion in that direction.
More specifically, a pawl is a movable component that operates as a lever. The pawl includes protuberances or other projections that engage the teeth of the ratchet wheel. The pawl is used to control the direction of the ratchet wheel rotation. In various embodiments, bolt engaging components may be used to apply pressure to a pawl (e.g., a spring loaded component) to keep a pawl engaged within the teeth of the ratchet wheel. A pawl may be machined, stamped or molded and constructed of one or more components having singular or multiple protuberances or projections.
Generally, a ratchet wheel is similar to other types of gear wheels. The pawl, which is usually spring-loaded to keep it engaged with the teeth of the ratchet wheel, will, when the ratchet wheel is rotated in one direction, slide up or “climb” the one side of a tooth. The pawl will then “jump” down into the bottom of the tooth space after going over the tip of the tooth, and the spring will have pushed it there. It will then ride up the slope of the next tooth as the ratchet wheel moves in the same “forward” direction. If the ratchet wheel is rotated in a “backward” direction, however, the pawl will only allow movement until it comes in contact with the opposite side of the next tooth back and it will jam there. This will limit backward movement of the ratchet wheel to a tooth length and no more, as long as the pawl is acting as intended to check the backward rotation.
One problem generally known in the art of box type wrenches using ratchet and pawl systems is that they are limited to a “nominal ratcheting arc,” which is defined by the number of teeth on the ratchet gear divided into 360 degrees. Various attempts are known in the art to create a reduced ratcheting arc ratchet wrench. However, these wrenches require a large rotational degree in order to use the wrench which is not possible in confined spaces. The need for such a large rotational movement lessens the utility of such wrenches. If a large degree of motion is required to rotate the ratchet, the wrench cannot be used in small or tight spaces. Attempts are also known in the art to create more efficient ratcheting mechanisms.
Accordingly, and in the view of these inventors, a need exists for a reduced ratcheting arc ratchet wrench assembly that can rotate a ratchet within small degrees. Further, it would be highly desirable to introduce a reduced ratcheting arc box end wrench and ratchet drive wrench using a ratchet and multiple pawl system that can operate at small rotational degrees and can be affordably manufactured and mass produced.
The present invention is a reduced arc box end ratchet wrench or a ratchet drive wrench which utilizes a multiple pawl ratchet assembly comprised of a box end wrench and ratchet drive wrench body or housing having an insert cavity to enclose critical components of an insert that is secured within the ratchet assembly. The insert is significant in that it can be press-fit or otherwise set into the wrench body or housing. The insert further includes at least two pivotal pawls. Each pawl comprises a pawl lever arm, the pawl lever arm being an elongated portion of the pawl. Further, each of the pawl lever arms has an outer end within which ratchet engaging teeth are formed. The pawl arms are positioned at critical angles of “pawl swing arc,” which is the location of the axis of rotation of identical pawls from the center axis of a ratchet wheel as it relates to tooth depth. In this way, the ratchet engaging teeth of each of the pawl lever arms alternately or successively engage a portion of the teeth of a ratchet wheel at all times.
This configuration allows smaller wrench rotation (or “ratcheting arc”) of down to 2.5, 1.75, or lower, degrees required to apply torque. The present invention further allows for a multiple pawl assembly. In the view of these inventors, a multiple pawl assembly is advantageous because it overcomes the geometrically defined restriction of the number of teeth on a ratcheting gear wheel as a limitation to achieving a reduced ratcheting arc. The advantage is achieved insofar as alternately or successively engaged pawls do not require the gear wheel to travel the complete increment of one gear tooth to engage the gear. Prior art limits the nominal ratcheting arc by dividing the number of teeth on the gear into 360. For example, with a gear having 72 teeth, the nominal ratcheting arc results in a 5 degree ratcheting arc (i.e. 360 degrees÷72 teeth=5 degrees per tooth).
The “reduced ratcheting arc” as described and claimed in the present invention defines the nominal ratcheting arc as follows: 360 divided by the number of teeth on the gear divided by the number of alternately or successively engaging pawls. For example, for a two pawl assembly, the equation would be as follows:
360 degrees÷72 teeth=5 degrees.
The 5 degrees is then divided as follows:
5 degrees÷2 pawls=2.5 degrees ratcheting arc.
For a three pawl assembly, the 5 degrees is divided as follows:
5 degrees÷3 pawls=1.75 degrees ratcheting arc.
For a four pawl assembly, the 5 degrees is divided as follows:
5 degrees÷4 pawls=1.25 ratcheting arc; and so on.
The foregoing and other features of the box end wrench and ratchet drive wrench of the present invention will be apparent from the detailed description that follows.
Referring now to the drawings in detail, wherein like numbered elements refer to like elements throughout,
Referring now to
In the exemplary embodiment shown, the pawls 90 are preferably like-configured components as illustrated in
Again referring to the illustrated embodiment in
The second, or toothed, end 93 of each pawl 90 extends slightly beyond the curved edge 44 of the insert 40. In this position, the pawl ends 93 and ratchet engaging teeth 94 can engage teeth 78 of the ratchet gear 70. The ratchet gear 70 is disposed within a circular ratchet gear aperture 24 of the body 20. Again, see
As shown in the exemplary embodiment of
Further, as shown in
Unique to the box end ratchet wrench that is configured with the “reduced ratcheting arc” of the present invention is placement of the pawl 90. As discussed at the outset of this disclosure, the “reduced ratcheting arc” can be calculated, as can the “pawl swing arc.”
Fundamental to the present invention is the claim that, with a given gear 70 and a given number of pawls 90, the ratcheting arc of the gear 70 can be reduced in proportion to the number of pawls 90, i.e. the “reduced ratcheting arc.” To achieve this, the present invention employs a unique system of placement of the pawls 90 around the circumference of the gear 70 in accordance with the following equations:
In the above equations,
For an assembly 10 utilizing two pawls 90, another way to consider the foregoing is to consider that the tooth 94 of one pawl 90 will be nearly perpendicular to a tooth 78 of the gear wheel 70. See
For a wrench 100 utilizing three pawls 90, the tooth 94 of one pawl 90 will be nearly perpendicular to a tooth 78 of the gear wheel 70. The teeth 94 of the other pawls 90 will be at a position nearly one-third or two-thirds the length or depth of another tooth 78 of the gear wheel 70. Significantly, this allows for alternate or successive engagement of the pawls 90. As used herein, the term “successive engagement” means to engage more than two pawls 90 at successive positions on the ratchet gear 70 during a series of rotational movements in one direction. For a wrench 100 utilizing four pawls 90, the tooth 94 of one pawl 90 will be nearly perpendicular to a tooth 78 of the gear wheel 70. The teeth 94 of the other pawls 90 will be at a position nearly one-fourth, one-half or three-fourths the length or depth of another tooth 78 of the gear wheel 70. Similarly, for a wrench utilizing five pawls 90, the same concept will apply and any of the multiple pawl configurations will allow for alternate or successive engagement of the pawls 90 in accordance with the present invention.
For the purpose of promoting an understanding of the present invention, the aforementioned references made to exemplary embodiments of a box ended ratchet wrench and the ratchet drive are made to demonstrate that the multiple pawl assembly is not limited to only two, three, four or five pawls 90. In addition, it is within the scope of the present invention that the pawls of the present invention could be collectively and alternatively configured as a brush-like structure having many bristles or “teeth” such that their engagement with the ratchet gear 70 is effected by substantially more contact with the teeth of the ratchet gear 70 and almost infinitesimal incremental movement of the ratchet gear 70 thereby. Further, the invention is not limited to the material used to fabricate the bristles or teeth that would engage the ratchet gear 70. The surface of the ratchet gear 70 at its outer circular perimeter could be configured with structures other than teeth as well.
It should also be understood that no limitations on the scope of the invention are intended by describing these exemplary embodiments. One of ordinary skill in the art will readily appreciate that alternate but functionally equivalent box ended ratchet wrenches and ratchet drives with multiple pawl assemblies may be used. The inclusion of additional elements may be deemed readily apparent and obvious to one of ordinary skill in the art. Specific elements disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to employ the present invention.
It should also be understood that the drawings are not necessarily to scale. Instead, emphasis has been placed upon illustrating the principles of the invention.
This application is a continuation-in-part of U.S. patent application Ser. No. 13/300,494 filed Nov. 18, 2011 now U.S. Pat. No. 8,567,287; which is a continuation-in-part of U.S. patent application Ser. No. 12/419,791 filed Apr. 7, 2009, now abandoned. The subject matter of these applications is incorporated herein by reference.
Number | Name | Date | Kind |
---|---|---|---|
5450773 | Darrah | Sep 1995 | A |
5630342 | Owoc | May 1997 | A |
6151993 | Shiao | Nov 2000 | A |
6209423 | Shiao | Apr 2001 | B1 |
6282990 | Miner | Sep 2001 | B1 |
6408722 | Chen | Jun 2002 | B1 |
6510765 | Mu-Lin | Jan 2003 | B2 |
6745647 | Wang | Jun 2004 | B2 |
7062994 | Chen | Jun 2006 | B2 |
7587961 | Chiang | Sep 2009 | B1 |
20070107560 | Chiang | May 2007 | A1 |
20100162486 | Joyce | Jul 2010 | A1 |
20100269639 | Sroka | Oct 2010 | A1 |
20120060652 | Gapp et al. | Mar 2012 | A1 |
Number | Date | Country | |
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20120167723 A1 | Jul 2012 | US |
Number | Date | Country | |
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Parent | 13300494 | Nov 2011 | US |
Child | 13416082 | US | |
Parent | 12419791 | Apr 2009 | US |
Child | 13300494 | US |