Technical Field

This invention relates generally to adjustable wrenches wherein movable elements are used to provide quick adjustment. This invention is most suitable for quick adjustable wrenches of the type wherein the jaws extend longitudinally from the handle. This type of wrench is generally referred to as an open-end adjustable wrench.

Background Prior Art

In the most common typed of adjustable wrench a worm gear and a journaled jaw member interact to change the relative location of the fixed and movable jaws. A pin rotatably holds the worm gear in a slot that extends through the handle of the wrench. The worm gear contacts a journaled rear portion of the movable jaw. The movable jaws slides in a groove defined by the handle to a location controlled by the worm gear. U.S. Patent 2,722,150 shows the general arrangement of this type of wrench. The worm gear arrangement of this typical wrench design always leaves some play between the jaws. This play results in the wrench sometimes slipping under pressure and thus detracting from the reliability of such devices.

Many adjustable wrench designs have been proposed that attempt to improve the adjustability and reliability of such wrenches. Such wrench designs include U.S. Patent 1,397,214 wherein a slot in the handle of wrench retains a grooved wedge that is spring biased towards a slidably mounted movable jaw having complimentary grooves for holding the jaw in position. The movement of the wedge is relative quick which in turn allows quick adjustment of the wrench. A number of other quick adjustment wrench designs use a series of wedges or ramps to quickly adjust the position of the movable jaw. Basic wedge designs in adjustable wrenches are well known and depicted in U.S. Patents 1,511,526, 1,481,250, 1,004,561, 1,514,017 and 1,427,918. Examples of wedge designs adapted for use in open end adjustable wrenches are shown in U.S. Patents 2,948,175 and 1,389,487 wherein a wedge cooperates with an inclined surface to move the wedge forward in compression against an opposing surface of the lower jaw. Pressure exerted by the wedge locks the jaw in place until displacement of

the wedge along the surface of the ramp releases the jaw. Another wedge-type wrench design is shown in U.S. Patent 4,903,556 were a wedge is contained in an inclined slot that extends through a handle portion of the wrench. The wedge has a flat surface on one side that acts against a surface of the slot and a tapered surface that acts against a tapered surface on the back of a movable jaw.

Although the wedge-type wrench designs offer quick adjustment and generally less play than the worm gear type wrenches, the wedge-type designs can be cumbersome to use and can still slip under heavy load. In these wedge type designs the wedge acts against the wall of the slot. Pressure on the wedge causes the wedge to move or give slightly. This small amount of give still results in slippage of the wrench that deforms nuts and bolts and can cause injury to the user. In addition very high loadings on many of these wedges can cause the wedge to jam and make readjustment of the wrench difficult.

One object of this invention is to provide a quickly adjustable wrench of the open-end adjustable type that has a reduced amount of play between the jaws relative to other open type adjustable wrench designs. Another object of this invention is to provide a quickly adjustable open-end wrench having a reduced number of parts and a simplified design.

To this end, it has been discovered that the problem with the other open-end adjustable type wrench designs that use a wedge in a slot for quick adjustment is that the wedges are always arranged in a way that will tend to enlarge the slot. As this enlarging

occurs, the wedge can slip slightly or a small relative movement of the jaws will occur, thereby causing the wrench to become loose. Particular arrangements of this invention can overcome these problems inherent in most wedge-type designs.

Summary of the Invention

The wrench of the first embodiment of this invention does not use a wedge, but rather uses two contact surfaces, typically in a form to provide point contact, on the movable jaw that surround a guide bar or are trapped in a guide slot. When the contact surfaces surround a guide bar, the points are spaced apart by a minimum distance slightly greater than the width of the guide member. Contact surfaces trapped in a guide slot are separated by a maximum width slightly greater than the width of the slot. By controlling the distance between contact surfaces, the movable jaw will bind against the guide member. This binding holds the jaw in place when it is under load. Once the load is removed the jaw is readily moved and readjusted to a new position.

In this first embodiment of this invention arranging the contact surfaces or points to bind the movable jaw around a solid jaw guide prevents slippage of the lower jaw and relative movement between the jaws thereby virtually eliminating the tendency of such wrenches to loosen under load. This first embodiment of this invention binds the movable jaw through a tension member that provides the two contact surfaces and passes through or straddles a solid jaw guide. The jaw guide extends in a direction generally perpendicular to the gripping surfaces of the jaws. Force on the moveable jaw causes the contact surface to act in compression on the lower jaw guides. Compression on the guide increases the binding action and keeps the movable jaw in place. A very simple wrench arrangement provides the necessary binding action. Consequently, by this arrangement. Applicant has discovered a simple adjustable wrench design wherein slippage of the wedge and consequent loosening

of the adjustable wrench is essentially eliminated by a simplified and easy to use design.

In the first embodiment of this invention, there is an adjustable wrench design having only two movable elements that uses contact surfaces fixed to a movable jaw to hold the movable jaw in position. The contact surfaces act on a guide member to bind the adjustable jaw from movement when the wrench is under load. Simple rotation of the movable jaw, once the load is removed, permits ready movement of the jaw to a new position.

Accordingly, this first embodiment of this invention is an adjustable wrench comprising a handle portion and a head portion formed at one end of the handle portion, the head portion having a fixed jaw extending outwardly from the head portion, the jaw having a first gripping face and a jaw guide located adjacent to the head, the jaw guide comprising a member providing first and second guide surfaces with one of the surfaces located on the front of the guide and the other surface located on the back of the guide. The wrench also includes a movable jaw having a second gripping face, a tongue extending from and fixed with respect to the movable jaw, first and second contact surfaces fixed with respect to the tongue, the first contact surface being positioned for contact with the first guide surface and the second contact surface being positioned for contact with the second guide surface, the tongue having at least one of the contact surfaces fixed thereto, the movable jaw having a first position relative to the handle portion permitting sliding motion between the fixed jaw and movable jaw and a second position relative to the fixed jaw wherein force on the movable jaw binds the movable jaw and prevents relative movement between the movable jaw and the fixed jaw.

In a second embodiment of the invention, an adjustable wrench comprises a handle portion and a head portion formed at one end of the handle portion. The head portion has a fixed jaw extending outwardly from the head portion. The jaw has a first gripping face and a jaw guide located adjacent to the head. The jaw guide comprises a rigid bar having a constant width and extends orthogonally away from the fixed jaw member. The jaw guide provides a first guide surface facing the fixed jaw and a second guide surface facing away from the fixed jaw.

A movable jaw has a second gripping face, and a tongue extending from the back of and fixed with respect to the movable jaw. A first contact point formed on the back of the movable jaw is located opposite the first guide surface. And, a pin extends transversely through a distal portion of the tongue and is located opposite the second guide surface. The pin provides a second contact point. This second contact point has an offset position with respect to the first contact point such that the second contact point is located closer to a plane containing the second gripping face than the first contact point and the first and second contact points are separated by a distance such that the second gripping face is substantially parallel to the first gripping face when the contact points are in contact with the jaw guide. In a third embodiment of this invention, a wedge element.is employed. Specifically, it has been found that arranging the wrench to clamp the movable jaw and a wedge about a solid jaw guide prevents slippage of the movable jaw and relative movement between the jaws, thereby virtually eliminating the tendency of such wrenches to loosen under load. Where a wedge is employed, this invention joins the jaw and the wedge through a tension member that passes through,

or straddles, a jaw guide. The jaw guide extends in a direction generally perpendicular to the gripping surfaces of the two jaws. The action of the movable jaw on the wedge pulls the wedge toward the jaw guide and places the guide in compression. Compression on the guide increases the clamping action and keeps the jaw in place. A relatively simple wedge arrangement provides the necessary clamping action. Consequently, Applicant has further discovered a simple adjustable wrench design wherein slippage of the wedge and consequent loosening of the wrench is essentially eliminated.

Moreover, this arrangement that employs a wedge provides a structural design that increases the clamping action of the wedge when the wrench applies torque to an object. Applying a torque with the wrench tends to separate the jaws, thereby developing a transverse force and the force couple between the jaws. The wedge arrangement of this invention causes both the transverse force and the force couple to tighten the clamping action of the wedge. Conversely in the open- ended wrench designs of the prior art, both the transverse force and force couple served to loosen the wedge. Accordingly, in the third embodiment of this invention, an adjustable wrench includes a handle portion and a head portion formed at one end of the handle portion. The head portion has a fixed jaw with a gripping face extending outwardly from the head portion and a jaw guide located adjacent to the head and comprising a solid member having first and second guide surfaces with one of the guide surfaces located on the front of the guide and the other surface located on the back of the guide. A wedge element having first and second divergent wedge surfaces is disposed such that the first wedge surface is in sliding contact with

the second guide surface. The wrench also includes a movable jaw having a gripping face disposed substantially parallel to the gripping face of the fixed jaw, a tongue extending transversely to the jaw guide and cooperating with the jaw guide for sliding motion along the length of the jaw guide, and first and second opposing jaw surfaces associated with opposite ends of the tongue and disposed such that the first jaw surface is in sliding contact with the second wedge surface and the second jaw surface is in sliding contact with the first guide surface.

In a variation of this third embodiment of this invention, the wrench comprises a handle portion and a head portion formed at one end of the handle portion. The head portion has a fixed jaw with a gripping face extending outwardly from the head portion in a direction generally longitudinal to the handle and has a jaw guide comprising two parallel bars located adjacent and extending perpendicularly with respect to the head. The two bars have a front surface facing the head portion of the wrench and extending from the head portion of the wrench and a back surface facing the handle end of the wrench and tapered away from and toward the handle end of the wrench at an angle of from about 0.5° to 2.5°. A tapered wedge having first and second divergent wedge surfaces defining an included angle of about 5° to 20° between the wedge surfaces is disposed such that the first wedge surface is in sliding contact with the back surface of the two bars. A slot extends through the wedge and has an opening on the first and second wedge surfaces. A movable jaw having a gripping face is disposed substantially parallel to the gripping face of the fixed jaw. The movable jaw includes a single tongue having a proximate end fixed to the movable jaw and a distal end located opposite the movable jaw. The tongue extends between

and transversely to the two bars of the jaw guide, through the slot and cooperates with the two bars for sliding motion relative thereto. The movable jaw further includes a first jaw surface that is located orthogonally to the gripping faces of the jaws, extending outwardly from the sides of the tongue at the proximate end of the tongue and disposed in sliding contact with the front surface of the two bars. A pin extends transversely outward from the sides of the tongue at the distal end of the tongue and is disposed for contact with the second wedge surface. Means are further provided for gripping the tapered wedge to move the wedge and release the movable jaw.

Additional embodiments, details and aspects of this invention are set forth in the following detailed description of the invention.

Brief Description of Drawings

Figure 1 is a three-dimensional view of the head portion of a first embodiment of the wrench of this invention; Figure 2 is a plan view of the wrench head of

Figure 1;

Figure 3 is a three-dimensional view of the head portion of a second embodiment of the wrench of this invention; Figure 4 is an exploded isometric view of a third embodiment of the wrench of this invention; Figure 5 is an assembled view showing a cross-section of the wrench head of the wrench in Figure 4 in an open and a closed position; and, Figure 6 is a cross-sectional view of the wrench in Figure 5 taken along line 6-6 in Figure 5.

Detailed Description

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. An adjustable wrench in accordance with this invention is shown in Figures 1-6. Two embodiments of this wrench are shown in Figures 1-3 and a third embodiment, that incorporates a wedge, is shown in Figures 4-6. For clarity, similar components are generally similarly labeled. Accordingly, the first two embodiments use reference numbers under 100 and the latter, third embodiment uses similar reference numbers in the 100-series.

An adjustable wrench 10 in accordance with the first embodiment of this invention is shown in

Figure 1. The wrench includes a handle portion 12 and a head portion 14, formed at one end of the handle, that provides a fixed jaw 16. A flat face 22 of the fixed jaw 16 provides a gripping surface. A jaw guide 20 projects in a generally transverse direction away from the flat face 22 of the head portion 14. The head portion 14 defines a slot in the form of a window 18 in the head portion 14, the slot being located to the inside of the jaw guide 20. The guide 20 has a first guide surface 23 on an outer surface of the head 14 and a second guide surface 24 bordering the window 18. The jaw guide 20 comprises two parallel guide bars 20a separated by a slot 26. This slot 26 extends across the width of the jaw guide 20 between the window 18 and the first guide surface 23.

The slot 26 has generally parallel sides that receive a tongue 28 of a movable jaw 30. The movable jaw 30 has a flat face 32 that provides a gripping surface. A contact point 36 at the back of the movable jaw 30 extends outwardly to sides of the tongue 28 at the junction of the tongue 28 with the jaw 30 and cooperates with a first guide surface 23 when the tongue 28 is positioned in the slot 26. The contact point 36 acts against the guide surface 23 when the jaw 30 is rotated away from the fixed jaw 16.

When positioned in the slot 26, the tongue 28 extends past a second guide surface 24 and into a window 18. The tongue 28 defines a hole 50 that receives a pin 48. The pin 48 functions to provide a back or second contact point that acts against the second guide surface 24 when the movable jaw 30 is rotated away from the fixed jaw 16.

To use this wrench, the flat surface 22 of the fixed jaw 16 is placed against an object for gripping. The user adjusts the wrench by sliding the movable jaw 30 toward the upper, fixed jaw 16 and into contact with the object, to be gripped. Once the movable jaw 30 contacts the object, it stops and the wrench is adjusted. In order to hold the adjustment of the movable jaw 30 when not in contact with an object, a small spring can be arranged to maintain a light pressure on the movable jaw. This small spring will allow removal and recontact of the wrench with the same object without repeated adjustment. Although not wishing to be bound by a theory, it is noted that when the wrench 10 grips an object, applying force to the wrench handle 12 tends to force the jaws 16,30 apart. The resulting downward pressure causes the contact points 36,48 to pinch the guide 20 and bind the movable jaw 30 so that it cannot move away from the upper fixed jaw 16. As the user pushes

against the movable jaw 30, it creates a force F_ that acts downwardly when the wrench is oriented, as shown in Figure 2. Frictional forces F ₂ act along the jaw guide 20 to resist the force F_ . The eccentricity of the force F_ from the jaw guide 20 creates a moment about the jaw guide that result in a force couple F ₃ and F that act against the lower portion of the jaw guide, as shown in Figure 2. The action of forces F ₃ and F ₄ exert a binding pressure on the jaw guide 20. Since in the design of the wrench of this first embodiment, as shown in Figure 2, all of the binding forces act compressively on the jaw guide 20, there is little deformation of the guide from the binding forces. Thus, the window 18 does not open under the load and significant rotation of the movable jaw 30 is prevented. The jaw guide 20 will have to resist shear forces imposed by the force couple F ₃ and F ₄ ; however, the deformation produced by resisting such loadings will be substantially less than the deformation associated with opening of the slot in the prior art arrangements.

This invention permits the jaw guide to be a simple solid member. The jaw guide can include one or more of such solid members. No special form is needed for the jaw guide, any simple cross-section can be used for the guide. Preferably, the cross-section of the guide members is convex, and more preferably square or rectangular in cross-section. It is particularly advantageous that the guide of this invention needs no dove tail or ^" other type of complex slot arrangement as part of the guide design. In addition, in this embodiment, the invention includes only two moving parts, the handle portion and movable jaw.

Important elements for the successful operation of this wrench of this first embodiment are the positioning of the contact points 36,48 and the

spacing between the contact points relative to the width of the guide member 20. The minimum spacing between the contact points 36,48 must exceed the width of the guide member 20 so that the movable jaw 30 slides freely when it is rotated toward the fixed jaw 16. For the purposes of this invention, the distance between contact points means the minimum distance between the actual contact surfaces and not the centerline distances between the pins. In order for the contact points 36,48 to bind the lower jaw 30 from movement, the contact points are offset at an angle of greater than 0° , but not greater than 30°, measured parallel to the plane of the gripping face (flat face 32) . This angle is shown as angle A on Figure 2 and defined by line B and line C. Angle A is preferably set at 15 ^β . The relative offset of the contact points 36,48 from the plane of the gripping face 32 works in conjunction with the angle to increase the distance between the contact points relative to the guide bar 20a when adjusting the movable jaw 30 and to bind the contact points and the jaw guide 20 when a force pushes against the gripping face 32. The contact points 36,48 are preferably arranged so that the face 32 of the movable jaw 30 rests parallel to the face 22 of the fixed jaw 16 when the contact points are in contact with the guide 20.

The binding force between the contact points 36,48 is inversely proportional to angle A. Thus, angle A must remain relatively small in order to properly restrain the movable jaw. If angle A becomes too large, the resulting force couple will not create enough frictional force to resist the downward load of the force F_ . Although the greatest force will be created when the angle A approaches 0° , such an arrangement would create a very high force couple leading to deformation of the jaw guide, the contact

points or both. This deformation can again cause the slippage which this invention seeks to eliminate. Therefore, angles of less than 30° and greater than 10° have been found to work best. The use of rounded contact points, as shown in Figures 1 and 2, promote easy adjustment of the wrench. Although this invention does not depend on any particular type of contact points, the rounded contact points provide a small amount of contact area. Accordingly, only a small rotation of the wrench is needed to free the lower, movable jaw, and the offset distance may be kept relatively small. However, in the case of very large loadings or small values of angle A, additional contact point surface area may be desired to prevent contact point or guide deformation that can cause the wrench to slip. Contact point area may be increased by simply using a flat surface of desired width instead of a rounded contact point. It is also possible to use a wedge element at the contact point surface to distribute the bearing pressure of the contact point loading.

Figure 1 shows a pin 48 that provides the back contact point. In addition to providing a radius, the pin 48 has the added advantage of providing a retainer for the movable jaw 30. To assemble the wrench 10, the tongue 28 is inserted through the slot 26 and the pin 48 is pressed into the hole 50. The wrench 10 is easily assembled using the pin 48 as a single locking element. The pin 48 also has a length that exceeds the thickness of the wrench so that the ends of the pin extend past the sides of the wrench. Projection of the pin ends past the sides of the wrench provides a convenient place to grip the movable jaw and slide it into gripping position. In this version of the wrench, where there is only one contact point within the slot or window 18, sliding of the movable

jaw 30 is facilitated by gripping the back of the movable jaw.

Apart from the arrangement and sizing of the contact points with respect to the guide member, other details of the wrench design of this first embodiment are not critical. Moreover, those skilled in the art will be aware of many variations in the design of the wrench that can be employed to accomplish the same results as those obtained by the wrench depicted in Figures 1 and 2.

In fact, from a fabrication standpoint, it may be preferred that the tongue of the movable jaw not pass through the slot in the jaw guide. It may be easier to form the movable jaw with a pair of tongues or webs that straddle a solid guide bar or jaw guide in place of the arrangement of Figure 1, where a single jaw tongue occupies the slot between two guide bar sections. When using the double tongue or web arrangement for the movable jaw, a single pin at the back of the movable jaw can occupy the slot or window and bridge the gap between the tongues or webs to retain the movable jaw with the wrench handle. Apart from the necessary changes in form, the function of the solid guide, contact points and slot 18 would remain essentially the same in either arrangement.

Additionally, it is not necessary to have the contact points acting against opposite sides of a solid member [jaw guide 20], as shown in Figure 1. Another arrangement for the wrench has the contact points acting against opposite walls of a slot into which the tongue extends. In a second embodiment of the invention, the wrench 10', shown in Figure 3, operates by the same principles as that shown in Figures 1 and 2, except that the guide member now comprises a window 52 defined by a head portion 14'. A movable jaw 30' has a tongue 28' that extends through a slot 26* into

the window 52. A pair of pins 54 and 56 are pressed through holes 58 and 59 in the tongue 28' to provide contact points. The first contact point 54 acts against a first wall 60 of the window 52 and the second contact point 56 acts against a second wall 62. Where the contact points 54,56 act in window 52, the first contact point 54 is offset above the second contact point 56. Apart from this different offset arrangement, all of the other design criteria for the contact points is the same as that described in conjunction with the first embodiment of this invention, shown in Figures 1 and 2.

An adjustable wrench 110 in accordance with a third embodiment of this invention is shown in Figures 4, 5 and 6. The wrench of the third embodiment 110 includes a handle portion 112 and a head portion 114, formed at one end of the handle, that provides a fixed jaw 116. A flat face 122 of the head 116 provides a gripping surface. A jaw guide 120 projects in a generally transverse direction away from the flat face 122.

The head 114 defines a window 118 in the head portion located to the inside of the jaw guide 120. The jaw guide 120 has a first guide surface 123 on an outer surface of the head 114 and a second guide surface 124 bordering the window 118. The jaw guide 120 comprises two parallel guide bars 120a separated by a slot 126 extending across the width of the guide between the window 118 and the first guide surface 123. The slot 126 has generally parallel sides that receive a tongue 128 of a movable jaw 130. The movable jaw 130 has a flat face 132 that provides a gripping face which cooperates with the flat face 122 of the fixed jaw 116. Guide surfaces 136 at the back of the movable jaw 130 extend outwardly at the junction of the tongue 128 with the jaw 130 and cooperate with

the first guide surface 123 to hold the flat face 132 of the movable jaw 130 generally parallel with the face 122 of the fixed jaw 116 when the tongue 128 is positioned in the slot 126. When positioned in the slot 126, the tongue

128 extends past the second guide surface 124 and into a channel 138 of a wedge block 140. The wedge block 140 has first wedge surfaces 142 that slide along and cooperate with the second guide surfaces 124. Opposite the first wedge surfaces 142, the wedge block 140 defines tapered, second wedge surfaces 144. The tongue 128 extends past the tapered surfaces 144 and traps the wedge block 140 between the second guide surfaces 124 and a pin 148. The tongue 128 defines a hole 150 that receives the pin 148. The pin 148 functions to provide an additional or second jaw surface. The wedge block 140 has a greater width than the head portion 114 so that transverse sides 146 project outwardly through the window 118 past the sides of the head portion 114. A recess 152 defined by the head portion 114 extends around the sides and the bottom of head portion 114 and receives a U-shaped sleeve 154 that retains the pin 148. The pin retainer 154 has slots 156 through which the wedge sides 146 extend when the retainer 154 is wrapped around the wrench head portion 114. A threaded hole 158 receives a screw 160 that passes through a hole 162 in the top of the retainer 154 to hold the retainer in place.

To use the wrench of this third embodiment, the flat face 122 of the fixed jaw 116 is placed against an object for gripping. The user adjusts the wrench by grasping the sides 146 of the wedge block 140 and by sliding the block 140 towards the fixed jaw 116. As the wedge block 140 moves toward the fixed jaw 116, contact of the pin 148 with the tapered surfaces 144 of the wedge 140 brings the flat face 132 of the movable

jaw 130 into contact with an opposing side of the object. Once the movable jaw 130 contacts the object, it stops and continued pressure on the wedge block 140 locks the movable jaw 130 into place against the object by the clamping action of the jaw guide surface 136 and the wedge surfaces 142 on the jaw guide 120.

The relative location of the wedge block and the movable jaw are shown in Figure 5. The elements without prime marks represent the relative position of the wedge block and movable jaw when the wrench is in an unlocked position and the primed numbers show the elements in a locked position.

Again, although not wishing to be bound by a theory, it is noted that when the wrench grips an object, applying force to the wrench handle 112 tends to force the two jaws 116,130 apart. The resulting downward pressure, as indicated on Figure 5 by F^ increases the clamping action of the jaw and wedge on the jaw guide 120. As the object pushes against the movable jaw 130, the force F_ acts downwardly when the wrench is oriented, as shown in Figure 5. Frictional forces F ₂ and bearing forces F ₂ acting along the jaw guide 120 resist the force F _x . The eccentricity of the force F_ from the jaw guide 120 creates a moment about the jaw guide that results in a force couple, idealized by F ₃ and F ₄ , that acts against the movable portion of the guide and the wedge in the manner as shown in Figure 2. The force F _x also acts downwardly through the pin 148, which increases the clamping action of the wedge 140 and the movable jaw 130 on the jaw guide 120. In addition, the action of the forces F ₃ and F ₄ increases the clamping force exerted on the guide jaw 120.

Since all of the clamping forces act compressively on the jaw guide 120, there is virtually no deformation of the guide from the clamping forces.

Thus, the window 118 does not open under load and rotation of the movable jaw 130 is reduced. The jaw guide 120 will have to resist shear forces created by the force F^* however, the deformation produced by resisting such loadings will be substantially less than the deformation associated with opening of the slot in the prior art arrangements.

Similarly, as with the previous embodiments of this invention, the jaw guide can be a simple solid member. The jaw guide of this third embodiment can include one or more of such solid members. No special form is needed for the jaw guide; any simple cross- section can be used for the guide. Preferably, the cross-section of the guide members is convex, and more preferably square or rectangular in cross-section. It is particularly advantageous that the guide of this embodiment needs no dovetail or other type of complex slot arrangement as part of the guide design.

The use of a movable jaw having relatively narrow depth D will tend to increase the magnitude of the clamping forces F ₃ and F*. However, any increase in the clamping force for a narrow depth movable jaw will be offset by the higher shear forces imposed on the guide as a result of the higher clamping forces. The effective offset distance between the force couple F ₃ and F ₄ also controls the clamping force. Figure 5 indicates this distance as OD. As OD decreases, the clamping force increases. However, as in the case of jaw length to jaw width, the benefit of higher clamping forces is offset by increased shear forces that tend to deform the guide. Consequently, the ratio of OD to D is usually at least 50%.

Certain aspects of the wedge block are important to the wrench function. There must be means for grasping the wedge block and unlocking the movable jaw. With the wedge block illustrated in Figures 4-6,

the user unlocks the movable jaw by sliding the wedge block 140 away from the fixed jaw 116. Sliding the wedge block 140 away from the fixed jaw 116 releases the pin 148 and allows the movable jaw 130 to move. In order to permit locking and unlocking of the movable jaw 130, the wedge block 140 and the second guide surface 124 must have the right taper. In order for the wrench to lock the guide surface that is in contact with the wedge block, i.e., the second guide surface 124 must have a small angle. This angle, labeled angle E on Figure 5, is usually in a range of from 0.5' to 2.5 " , with an angle of 1.5" being preferred. Smaller angles E are generally preferred to provide better locking of the movable jaw 130; however, a smaller angle E requires additional wedge block 140 movement to lock the movable jaw 130. The divergent surfaces of the wedge block, i.e., wedge surfaces 142 and tapered surfaces 144, also define a small included angle, labeled angle G in Figure 5, which is needed for the movable jaw 130 to lock and release. Angles G in the range of from 5* to 20° have been found to work, but wedge angles G in the range of 8 ^β to 12° are particularly preferred. It has been found that too small of an angle G will jam the wedge and prevent easy release of the movable jaw, while too large of an angle will hinder locking of the movable jaw and can result in its sliding under load. The wedge block design pictured in Figures 4 and 5 shows the wedge block having only the back side tapered at an angle G of 10°. Apart from the contact surfaces, taper angle and providing means for gripping, other aspects of the jaw and wedge block configuration of this third embodiment are not important. Although Figures 4-6 show the means for gripping the wedge block as comprising extended transverse sides 146, a number of other arrangements can be provided for allowing one to

grip the wedge block. For example, the sides of the window 118 can be left open to simply grab a wedge that is flush with the sides of the wrench. Such an arrangement would eliminate the sleeve for keeping the retaining pin 148 in place. Alternately, any suitable means can be employed to hold such a pin in place. In fact, the pin 148 can be eliminated altogether, as long as some form of stop is provided at the back of the tongue to act against the back side of the wedge. Or, the.wedge block can be in the form of a spiral cam pivotally supported by the pin. In such an arrangement, the cam would have a lever for locking and unlocking the movable jaw.

Moreover, those skilled in the art will be aware of many variations in the design of the wrench that can be employed to accomplish the same results as those obtained by the wrench depicted in Figures 4 and 5. For instance, the wedge need not be in the window at all. A pin or similar stop at the back of the tongue 128 can act directly against the inner surface of the guide and the wedge can act between the movable jaw and the outer surface of the guide. Furthermore, a pair of tongues or webs can replace the single tongue and straddle a solid guide bar in place of having a slot between two guide bar sections, as shown in Figures 4 and 5.

Figure 6 depicts the cross-section of the wrench of Figures 4 and 5 wherein the jaw guide straddles the tongue of the movable jaw. Such an arrangement is readily changed to one in which there is a front wedge block and a solid jaw guide bar. In such an arrangement, a movable jaw would define a pair of webs that straddle a solid guide bar formed as part of a wrench handle. The wrench handle would define a slot between itself and the solid guide bar. A pin would be fastened to the webs and extend through a slot to

secure the jaw to the wrench handle. The webs would also straddle a wedge block, which is trapped between the base section of the webs and the front of the guide. The wedge block would have the same angle as previously defined and the front of the guide would incorporate the angle E. Such a wrench will function in essentially the same manner as the wrench described in conjunction with Figures 4 and 5.

The description of this invention in the context of a limited number of specific embodiments is not meant to limit this scope of the claims to the details disclosed herein.