This invention pertains to ratchet wrenches, and more particularly, it pertains to a ratchet wrench having a fine adjustment mechanism for indexing or rotating the socket thereof without moving the free end of the wrench.
When using a ratchet wrench, the available space for movement of the handle is often less than the angle between the notches of the ratchet gear of the wrench. In the past, several inventions were developed to address this problem. The following publications represent a good inventory of the inventions found in the prior art describing tangential drive mechanisms, where a belt, a cable or a chain is wrapped around the ratchet gear of a ratchet wrench. The belt, cable or chain is worked from the free end of the wrench to rotate the ratchet gear with sufficient torque to drive a nut or a bolt to and from a face engagement thereof.
U.S. Pat. No. 2,288,217 issued to E. C. Trautman on Jun. 30, 1942;
U.S. Pat. No. 2,290,197 issued to H. H. Merriman et al., on Jul. 21, 1942;
U.S. Pat. No. 2,292,391 issued to H. H. Merriman et al., on Aug. 11, 1942;
U.S. Pat. No. 2,530,553 issued to J. D. Strobell on Nov. 21, 1950;
U.S. Pat. No. 2,733,745 issued to L. Norwood on Feb. 7, 1956;
U.S. Pat. No. 4,184,390 issued to J. P. Evans on Jan. 22, 1980;
U.S. Pat. No. 4,491,042 issued to J. E. Lopochonsky on Jan. 1, 1985;
U.S. Pat. No. 4,507,989 issued to R. W. Baker on Apr. 2, 1985;
U.S. Pat. No. 4,592,254 issued to F. A. Wallis on Jun. 3, 1986;
U.S. Pat. No. 4,867,016 issued to W. Di Edwardo on Sep. 19, 1989;
U.S. Pat. No. 7,320,267 issued to Y. T. Chen on Jan. 22, 2008;
U.S. Pat. No. 8,196,494 issued to T. E. Brovold on Jun. 12, 2012.
In another arrangement found in the prior art, a belt is positioned to enclose a nut. The belt is pulled from the end of a long handle to rotate the nut on a threaded stem.
U.S. Pat. No. 3,200,676 issued to A. B. Pagel on Aug. 17, 1965.
In yet another previous invention, the following document discloses a socket and a string wound around the socket for rotating a nut on a bolt from a remote location by pulling on the string.
U.S. Pat. No. 6,167,785 issued to V. Penner on Jan. 2, 2001.
While the inventions in the prior art deserve undeniable merits, there is a common inconvenience with the use of a tangential belt or cable enclosing a ratchet gear. This drawback is related to a phenomenon encountered with a cable wrapped around a drum. This phenomenon is often referred to as the principle of the capstan equation, where the tension of a cable or a belt wrapped around a drum may be different on either side of the drum. In fact a small force exerted on one end of the cable on one side of the drum can carry a much larger loading force on the other side of the drum. A double turn of a rope around the drum of a capstan for example can retain a large ship to a wharf, even when the other end of the rope is laying loosely on the deck of the ship.
This phenomenon is also encountered during the return cycle of a tangential drive ratchet wrench, when the belt, cable or chain must slip over the ratchet gear to return to its starting point. While some of the mechanisms found in the prior art have a spring attached to the return end of the belt, cable or chain, even a small tension on the pulling end can prevent the belt, cable or chain from sliding back.
A slight tension on the pulling end of the belt, during the return cycle of the belt, increases the friction force between the belt and the crest and driven segments of the ratchet gear. The resulting holding force is increased exponentially from that slight tension by a factor corresponding to the friction coefficient between the belt and the surface of the ratchet gear and the surface contact area of the belt with the ratchet gear.
For example, a lack of manual coordination by the user in releasing the pulling end of the belt can make it very difficult to operate the wrench. Any hesitation or muscular tremor in fully releasing the pulling end of the belt causes the belt to stick, to grab and to block halfway along the return cycle of the belt.
Because of this phenomenon, a tangential drive on a ratchet wrench experiences a poor performance every time the user is not in perfect synchronization with the speed and amplitude of the mechanism.
It is believed that this principle of the capstan equation occurring in tangential drive ratchet wrenches has contributed to diminish public confidence in tangential driven wrenches and as a consequence, this capstan equation effect has been detrimental in limiting the commercial success of these wrenches.
Therefore, it is believed that a market demand exists for a better design of a tangential drive ratchet mechanism, where the principle of the capstan equation has no negative effect on the operation of the mechanism.
In the present invention, there is provided a ratchet wrench with a fine socket-indexing mechanism that eliminates the capstan equation phenomenon. A second spring is provided to counteract the effect of the return spring and to remove any surface friction between the belt and the driven and crest segments of the ratchet gear. The tangential belt slides back easily on the driven, reverse and crest segments of the ratchet gear so that the operation of the wrench is smooth, positive and firm.
In a first aspect of the present invention, there is provided a tangential drive mechanism for a ratchet gear. The mechanism includes a ratchet gear having a driven segment, a return segment and a crest segment between the driven segment and the return segment. A belt is mounted around the ratchet gear. The belt has a driven end which is movable away from the ratchet gear for driving the ratchet gear in a rotational direction, and toward the ratchet gear during a belt return cycle. The belt also has a return end opposite the driven end. The return end also extends away from the ratchet gear. In this mechanism, a return spring is attached to the return end of the belt for applying a tension force on the return end. A return-assist spring is attached to the driven end of the belt for applying a compression force on the driven end of a same magnitude as the tension force, toward the return end. Because of this compression force, the belt has no surface pressure along the crest segment and the driven segment of the ratchet gear and can easily disengage from the ratchet gear during the belt return cycle. Because of this return-assist spring, basically, the capstan equation phenomenon is eliminated from this mechanism.
In another aspect of the present invention, there is provided a ratchet wrench having a stem and a box end at the end of the stem. The box end includes a socket mounted therein. A ratchet gear is mounted in the box end around the socket. The ratchet gear has a driven segment, a return segment and a crest segment between the driven segment and the return segment. A belt is mounted around the ratchet gear. The belt has a driven end movable away from the ratchet gear along the stem for driving the ratchet gear in a socket rotation direction. The driven end is movable toward the ratchet gear during a belt return cycle. The belt also has a return end opposite the driven end. The return end also extends along the stem, and is movable toward and away from the ratchet gear.
A return spring is attached to the stem and to the return end of the belt for applying a tension force on the return end. A return-assist spring is attached to the driven end of the belt and to the stem for applying a compression force on the driven end of a same magnitude as the tension force, toward the return end. In a same way as the mechanism previously described, the belt has no surface pressure along the crest segment and the driven segment of the ratchet gear and can easily disengage from the ratchet gear during the belt return cycle.
In yet another aspect of the present invention, there is provided a magnetic nut retainer for use with a box-end socket wrench having a nominal socket size. This magnetic nut retainer comprises a flange having an annular disc-like configuration, and a magnetic element having an annular disc-like configuration with hexagonal circumference. The magnetic element has magnetic properties. The magnetic element is smaller in outside diameter than the flange and it is affixed in a concentric manner to the flange. The magnetic element and the flange have a hole through their respective centers of a nominal size corresponding to the size of the socket. The hexagonal circumference of the magnetic element is smaller than the nominal socket size, and the flange is larger than the socket size for retaining the magnetic element inside one end of the socket.
In yet another aspect of the present invention, there is provided a method for operating the previously described ratchet wrench. This method comprises the steps of:
This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiment thereof in connection with the attached drawings.
A preferred embodiment of the ratchet wrench according to the present invention is described with the aid of the accompanying drawings, in which like numerals denote like parts throughout the several views:
The drawings presented herein are presented for convenience to explain the functions of all the elements includes in the preferred embodiment of the present invention. Elements and details that are obvious to the person skilled in the art may not have been illustrated. Conceptual sketches have been used to illustrate elements that would be readily understood in the light of the present disclosure. These drawings are not fabrication drawings, and should not be scaled.
Referring firstly to
Although a single box end 24 is illustrated and described herein, it will be appreciated that a duplication of the structure and elements described herein can be made to obtain a double-ended box wrench with a different socket size at each end.
Similarly, although a ratchet wrench is illustrated and described as the preferred embodiment of the present invention, the tangential drive system described herein can be applied to other mechanisms. For example, it is believed that the tangential drive system described herein can be used to operate an out-of-reach industrial gate valve, or other similar hard-to-access equipment having an actuator mounted to a threaded stem. Therefore, the tangential drive system described herein is not limited to ratchet wrenches.
The box end 24 of the preferred wrench 20 is made of an hexagonal socket 34 encircled by a ratchet gear (illustrated elsewhere) mounted therein. The ratchet gear is operable in one direction by a pawl-type latching device as is customary with ratchet wrenches.
Referring to
Other structural elements of the preferred wrench 20 are illustrated in
The ratchet gear 50 encircling the hexagonal socket 34 is illustrated in
A toothed belt 54, is mounted around the ratchet gear 50. Both ends of the belt 54 extend along the shank 30 of the wrench 20. The shank 30 of the wrench 20 has spring seats that have been milled away, one on each side of the shank 30. The return end 56 of the toothed belt 54 extends along a first spring seat 58. The driven end 60 of the toothed belt 54 extends along a second spring seat 62. For reference purposes, the first spring seat 58 is referred to as the return side spring seat 58, and the second spring seat 62 is referred to as the driven side spring seat 62. The spring seats 58 and 62 also designate the return side and the driven side of the wrench 20.
A return spring 64 has one end thereof attached to the return end 56 of the toothed belt 54, and a second end connected to a first anchor hook 66 at the far end of the return side spring seat 58 as can be seen in
The driven end 60 of the toothed belt 54 is attached to a sliding bar 70, which slides back and forth frictionless along the driven spring seat 62. The sliding bar 70 is linked to the slider body 26 by means of a dovetail engagement as can be seen at labels 72 and 72′ in
The slider body 26 is made of two halves 26′, 26″, which enclose the shank 30 of the preferred wrench in a sliding fit mounting. The movement “A” of the slider body 26 along the guide segment 28 is limited by the collars of a first 74 and second 76 sleeves mounted over the shank 30 of the preferred wrench 20. The movement “A” is about 1 inch to 1¼ inch. This distance “A” is equivalent to a comfortable movement of a user's thumb. Both sleeves 74, 76 are made of a rubberized plastic material, offering a comfortable grip on the preferred wrench 20.
Referring to
In the preferred ratchet wrench 20 with fine socket-indexing mechanism, there is provided a second spring 80 mounted along the driven side spring seat 62, between the slider bar 70 and the shank 30 of the wrench. This second spring 80 prevents the occurrence of the effect of the capstan equation as mentioned before. This second spring 80 is referred to as the return-assist spring 80. This return-assist spring 80 has one end connected to the attachment point 82 of the driven end 60 of the belt 54 to the slider bar 70 as it can be better seen in
Referring back to
The return spring 64 applies a tension force along the belt 54 along the first segment “B”. The spring 80 applies a same compression force on the belt along the third segment “D”. Both forces are oriented opposite from each other relative to the ratchet gear 50. Because both springs 64, 80 have same physical and elastic properties and a same elongation in use, there is substantially no surface pressure between the belt 54 and the crest segment “C” of the ratchet gear 50.
Although both springs 64, 80 work against each other relative to the ratchet gear 50, both springs 64, 80 contribute to apply forces in a same direction on the slider body 26, during both the driven movement and the return movement of the belt. Both springs 64, 80 apply forces in a same direction along the belt 54.
When the thumb knob 32 is pulled away from the box end 24 of the preferred wrench 20, the movement of the slider body 26 creates an unbalance between the springs 64 and 80 and causes the belt 54 to engage with the crest “C” and the driven “D” segments of the ratchet gear 50. A movement of the thumb knob 32 away from the ratchet gear causes the belt 54 to engage with all three segments “B”, “C” and “D” of the ratchet gear 50, to turn the ratchet gear in a clockwise direction.
When the thumb knob 32 is released, the return-assist spring 80 counteracts the tension force of the return spring 64, relative to the ratchet gear 50 causing the belt 54 to relax along the driven segment “D” and the crest segment “C” of the ratchet gear 50. Because the slider bar 70 slides along the wrench in a frictionless manner, the return-assist spring 80 pushes the belt 54 backward to force it to disengage from the ratchet gear 50 and to slide against the outside surface of the cavity in the box end 24 of the preferred wrench 20 as is illustrated in
The inside cavity of the box end 24 includes sufficient space to accommodate the ratchet gear 50, the toothed belt 54 and a clearance “E” between the tips of the teeth of the belt 54 and the tips of the teeth of the ratchet gear 50. As a result, the toothed belt 54 can slide over the ratchet gear 50 during the return cycle, without touching the gear 50, as shown by the clearance “E” in
The return spring 64 causes the belt 54 to slide easily over the return segment “B” of the ratchet gear 50. Because of the return-assist spring 80 basically, the capstan equation principle does not impede the operation of the preferred wrench 20. As a result, the operation of the preferred wrench is smooth, consistent and positive, without any sign of sticking or hesitation in its movement.
While one embodiment of the present invention has been illustrated in the accompanying drawings and described herein above, it will be appreciated by those skilled in the art that various modifications, alternate constructions and equivalents may be employed. Therefore, the above description and illustrations should not be construed as limiting the scope of the invention, which is defined in the appended claims.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/CA2015/000609 | 12/31/2015 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2016/112453 | 7/21/2016 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
2288217 | Trautman | Jun 1942 | A |
2290197 | Merriman | Jul 1942 | A |
2292391 | Merriman et al. | Aug 1942 | A |
2530553 | Strobell | Nov 1950 | A |
2603998 | Schwartz | Jul 1952 | A |
2726563 | Blackburn | Dec 1955 | A |
2733745 | Norwood | Feb 1956 | A |
2806396 | Miller | Sep 1957 | A |
3200676 | Pagel | Aug 1965 | A |
3368432 | Halls | Feb 1968 | A |
3640159 | Halls et al. | Feb 1972 | A |
3731722 | Carr | May 1973 | A |
3901107 | Halls | Aug 1975 | A |
4184390 | Evans | Jan 1980 | A |
4491042 | Lopochonsky | Jan 1985 | A |
4507989 | Baker | Apr 1985 | A |
4532833 | Downs | Aug 1985 | A |
4592254 | Wallis | Jun 1986 | A |
4656894 | Goetz | Apr 1987 | A |
4867016 | Di Edwardo | Sep 1989 | A |
5509705 | Woodsum | Apr 1996 | A |
5692789 | Woodsum | Dec 1997 | A |
5768957 | Baker | Jun 1998 | A |
6167785 | Penner | Feb 2001 | B1 |
6748826 | Marks | Jun 2004 | B2 |
6761092 | Hsien | Jul 2004 | B2 |
6789450 | Helfet | Sep 2004 | B1 |
7320267 | Chen | Jan 2008 | B1 |
7331259 | Chen | Feb 2008 | B1 |
8196494 | Brovold | Jun 2012 | B2 |
Number | Date | Country | |
---|---|---|---|
20180043511 A1 | Feb 2018 | US |
Number | Date | Country | |
---|---|---|---|
62125234 | Jan 2015 | US |