WO2007082238A2 - A functional polymer faced hammer for reduced vibration, noise, and improved ergonomics - Google Patents

Abstract

This invention consists of a polymer insert, which term can include a cap or face, added to a metal hammer to eliminate metal to metal contact on direct hits, and minimize metal to metal contact on indirect hits. The polymer insert is selected to be objectively 'tough,' in the sense of withstanding repeated impact, while transmitting force to hit an object while also not failing. The polymer insert is positioned between the hammer face and the item to be struck - usually a nail. The polymer insert can be secured to the hammer by: a rigid retainer sleeve, preferably of metal or plastic; a pressed-on shaped polymer cap; or a polymer insert pressed into a recess in the hammer.

Description

A FUNCTIONAL POLYMER FACED HAMMER FOR

REDUCED VIBRATION, NOISE, AND IMPROVED ERGONOMICS

CONTINUATION DATA

This application claims priority of U.S. applications US 60/766,315, filed on 10 Jan 2006, US 60/ 767,289 filed 15 March 2006 , PCT/US2006/037163 filed 25 Sept. 2006 and a provisional application of this name filed on 9 January, 2007 as US 60/884,168. This application is a cqntinuation-in-part for U.S. purposes of such applications and a claim for priority for purposes of any nation requiring a similar claim of priority.

FIELD OF INVENTION

This invention is for an ergonomic hammer with significantly improved safety and vibration and noise characteristics.

SUMMARY OF INVENTION

This invention consists of a polymer insert, which term can include a cap or face, added to a metal hammer to eliminate metal to metal contact on direct hits, while selecting a polymer that is "tough" in the sense of withstanding repeated impact, while also transmitting force and while not failing. The polymer insert is positioned between the hammer face and the item to be struck - usually a nail. The polymer insert can be secured to the hammer by: a rigid retainer sleeve, preferably of metal or plastic; a pressed-on shaped polymer cap; or a polymer insert pressed into a recess in the hammer. The polymer face thus presented on the metal hammer prevents metal-to-metal contact and thereby: reduces noise and vibration; improves ergonomics; improves safety because it reduces the risk of metal fragments from a hammer head or brittle nails and limits the risk of sparking, reduces marring, and enhances user comfort. The polymer cap is designed with special geometric features and a special polymer material so that it can transmit enough force to drive nails and perform other needed functions but is durable enough to survive repeated blows.

BACKGROUND Current Problems in Conventional Hammers

Very high impact forces are created when hammers drive nails or strike tools such as chisels. These impacts can create ergonomic problems for the user because they generate large vibrations that can cause physiological damage to hands and arms; and, they generate noise that can damage the ear and create hearing loss. In addition, fragments of hammers or nails can create serious injury to the user or bystander. Flying fragments are particularly hazardous when hardened masonry nails are used.

Another problem in existing hammers occurs when a user drives nails, but misses a direct hit. The hammer will then mar the surface material (e.g. wood, plasterboard).

State of current art

There are two primary methods that have been used of overcoming the ergonomic and safety problems in existing hammers: cushioned grips and personal protection items (safety glasses, ear protection).

In addition, marring can be reduced by hammers with broad faces or hammers made of plastic (for very low impact force), usually a moderately hard polymer, but these hammers are unable to obtain the durability, including the avoiding of shattering, while simultaneously achieving continued efficiency in driving nails or the like.

Attempted solutions:

A variety of solutions have been proposed.

The first class of solution is low vibration, shock absorbing hammers using modified handles.

Examples include: Gierer et al, U.S. Pat. 6,763,747 entitled "Shock Absorbing Hammer and Handle Assembly," 20 July 2004, which has elastomeric components added to the handle; Lai, U.S. Pat. 6,619,408, entitled "Hammer in Shock Resistant Arrangement," 16 Sept. 2003, which proposes a unique geometric structure in handle to absorb shock; Chen, U.S. Pat. 6,405,616 "Hammer with Shock Reduction Structure," 18 June 2002 which presented a modified hammer handle to absorb shock; Wu, U.S. Pat. 6,467,376, entitled "Hammer," 22 Oct. 2002 which proposed a composite structure used to connect the hammer head to handle to absorb shock; and Hebert et al, U.S. Pat. 5,490,437 entitled "Hammer," 13 Feb. 1996, which proposed a plastic handle including gelatinous material in core. The second general class of low vibration, shock absorbing hammers are those using modified hammer heads.

An example is Gierer, U.S. Pat. 6,128,977, entitled "Shock Absorbing Claw Hammer," 10 Oct. 2000 which uses a multicomponent head with articulating metal parts.

A third class of low vibration, shock absorbing hammers are those using shock absorbing layers inserted in a removeable metal cap. Examples are: The disadvantage, from the perspective of the inventors of the present invention, is that that hammer does not eliminate metal to metal contact and the attendant, chipping, marring and spalling.

Another class of low vibration, shock absorbing hammers are those using shock absorbing layers Cox, U.S. Pat. 6,463,832, entitled Capped Hammer Head, 15 Oct. 2002, and Cox, U.S. Pat. 6,457,384 entitled "Capped Head Hammer." In each of these inventions, a soft layer is inserted in a removeable metal cap. The '384 patent proposes a cap that is squeezed centripetally by a fastener, and further proposes the hammer have a pin that runs through the cap with the soft material and the hammer head and out the other side of the cap which pin loosely holds the so when the hammer strikes, the cap moves toward the hammer head cushioned by the soft material which reduces vibration.

Non Marring Hammers

There are many hammers with relatively soft impact faces (rubber, polymer, lead) commercially available for special purposes (e.g. low marring). An example of this type of hammer is the ultra high molecular weight polyethylene hammer by Metrocraft.

Hammers with Removable Caps

U.S. Pat. 7,104,874 entitled "Hammer Having a Detachable Bell," proposes a metal hammer cap attached to the hammer by mechanical means. As referenced earlier, Cox, U.S. Pat. 6,463,832, entitled Capped Hammer Head, 15 Oct. 2002, and Cox, U.S. Pat. 6,457,384 entitled "Capped Head Hammer," 1 Oct. 2002, propose a metal hammer cap attached to the hammer by mechanical means with a soft layer between the hammer head and the cap. Older technology, U.S. Pat. 2,518, 059 Aug. 1950 suggests a removeable hammer cap that is screwed on.

OBJECTS OF THE INVENTION

It is an object of the invention to eliminate metal to metal contact upon normal hammering, and to minimize metal to metal contact on side hits.

It is an object of the invention to reduce vibration of the handle, primarily by reducing vibration as a result of the selection of a polymeric material over the face of the hammer

It is an object of the invention to reduce marring by an off center hit.

It is an object of the invention to minimize loss transmission of force and therefore avoid loss of efficiency with the hammer.

It is an object of the invention to reduce noise and to eliminate the metal to metal ping from normal metal-to-metal hammering.

It is an object of the invention to accomplish these objectives with a material that resists shattering or damage that leads to shattering or failure while protecting the characteristic of force transmission.

DESCRIPTION OF FIGURES

Figure 1 shows the invention as a hammer with a polymer impact face having a polymer insert (1), on the face of the hammer (3) head secured by a retaining sleeve (2), preferably made of steel.

Figure 2 is a side view of the hammer in Figure 1.

Figure 3 is an exploded view diagram of Figure 1.

Figure 4 is a cross-sectional side view of Figure 1 and shows a distance d which is equal to the protrusion of the polymer face (1) beyond the retaining sleeve (2). Figure 5 is a cross-sectional view of an alternate mode of a polymer insert in the form of a polymer insert shaped as a polymer cap over the hammer and shows the rounded interior edges of the polymer insert corresponding to the impact face rounded edges.

Figure 6 is a cross-sectional view of a polymer insert shaped like a cap functioning as a cap on the hammer with a relatively wide cavity compared to the diameter of the hammer face into which cavity the polymer insert is set.

Figure 7 is a cross-sectional view of a polymer insert disposed on the hammer with a relatively wide diameter cavity compared to the diameter of the hammer face into which cavity the polymer insert is set.

Figure 8 shows a polymer insert disposed on the hammer with means for securing the polymer insert, in this instance, an annular ring or tab, interior to the polymer insert to retain the polymer insert.

Figure 9 shows a cross-sectional view of a tab or vertical indentation (9) disposed on the polymer insert in the form of the cap of Figure 5 interior to the insert to retain the cap on the hammer head.

PREFERRED MODES OF THE INVENTION

The invention significantly alleviates the current problems in hammers by adding a polymeric material in the form of an insert between the hammer head and the nail or tool being struck, with the preferred mode being to contain the polymeric material within a retaining sleeve or retaining ring. The polymer insert can be a specially shaped one- piece cap that has a sleeve that fits snugly on the hammer head. The hammer head can also have a recess or aperture within which is contained a polymeric material.

Alternatively, the polymer insert is attached to the hammer head by any of a number of methods. For example, a snap-on polymer cap, a polymer disk secured by a retaining ring or sleeve, or a polymer plug inserted in a recess.

The polymer insert is made of a material that can adequately transmit impact force and still survive repeated blows without damage. Nails present a particularly difficult problem. The polymer insert and material selected for its composition and the geometry of the polymer insert are designed to adequately drive nails and still survive repeated blows without failure. The shape of the polymer insert is designed to: minimize crack propagation; maximize force transmission, and, minimize surface marring from off- hits. The primary advantage of this invention over the prior art is that metal-metal contact is completely eliminated in a functional, nail driving, durable hammer. Since all metal-metal contact is eliminated, this new hammer has lower vibration, noise, and marring than current hammers. Many prior methods attempt to reduce vibrations from metal-metal impact by cushioning the effect, but none eliminate the metal-to-metal contact altogether. The current low marring hammers (as referenced above) do eliminate metal-metal contact, but they are not able to drive nails and withstand repeated hard blows. In addition, this invention includes a provision for removing and replacing the polymer insert.

There are many types of removable hammer caps disclosed in the prior art as referenced above, but these methods are not suitable for the polymer systems of this invention and cannot achieve both the results of durability and effectiveness of driving objects. The retaining ring in particular, as proposed by the inventors, has significant support characteristics for the polymer insert.

FURTHER DESCRIPTION

The basic invention is shown on Fig 1. A retaining sleeve (1) of metal or plastic, preferably steel, contains a polymer insert made of polymeric material shaped like a disk (2) juxtaposed to the impact face of a hammer head (3). In this mode, the polymer insert is disposed over the face of the hammer head portion of the invention which actually hits the object being struck or driven. The retaining sleeve is firmly pressed on the hammer head but can be removed if the polymer insert needs to be replaced. Alternatively, as in Figure 5, the polymer insert may be shaped like a cap to surround at least part of the hammer head so that it can be pressed on the hammer head against the hammer impact face and be retained by friction. In that case, a retaining sleeve is not needed. However, a retaining sleeve could be used to reinforce the face being impacted of the polymer insert shaped like a cap.

The invention is best used with a hammer, but is suitable for a one or two-faced mallet or sledge and for the face of maul wedge, or other striking device (collectively referred to as a hammer). The head of the hammer is referred to as the impact end. Normally, a handle is attached to the impact end, and there is at least one impact face on the hammer which is parallel to the handle. Some sledges or mallets have two opposite impact faces. That impact face is usually flat or crowned and has a hammer face side aligned approximately perpendicularly to the face. Normally the hammer face side is round on a standard carpenter's hammer.

The preferred polymeric material for the polymer insert is a Dupont Corporation (Wilmington, Delaware) product called Minion® (registered trademark of Dupont Corporation). The preferred material includes MINLON 11C40 and MINLON 12T. Impact resistant material for the polymer insert such as nylon is contemplated. Another preferred material is fiber reinforced material, or particle reinforced material, preferably mineral particle. Some of the materials have elastomeric tougheners. Materials useful in the invention are DuPont Zytel® polymers. The following Dupont materials are suitable: FN718, 80G33L, 8018, and ST801. The 8018 material seems preferable.

These materials have the addition version of being thermoplastic polymers which are easier to melt and shape, as opposed to thermosetting materials, which can also be used, but are hard to control in the molding process.

The polymer insert is positioned and sized in a way that does not alter the basic use of the hammer. The polymer insert can also be used on any unconventional or specialized hammer (e.g. spike maul) or other impact tool (e.g. impact wrench) or hand nailer. The polymer insert can be secured by having protrusions in the sides of the polymer insert, either longitudinal (perpendicular to the impact face) or circumferential, or on the hammer head, either longitudinal (perpendicular to the impact face) or circumferential. Alternatively, the cap can be attached to the hammer by mechanical means of fitting over or into grooves or by a suitable adhesive.

The geometry of a preferred mode of polymer insert is shown in more detail by the cross section shown on Fig 5. The geometric details are set in a number of ways. The interior shape of the cap matches the hammer head chamfer or rounding and is preferably rounded, and also the impact face. The interior edge of the polymer insert in the form of a cap as shown in Figure 5 is rounded preferably by a radius of at least .005 inches. In addition, the outside edge of the polymer insert shaped like a cap is rounded to a relatively large radius of .125 inches or 3mm and referred to as a rounded corner. To minimize crack formation on impact, all shape curvatures near the impact face surface are rounded. The insert thickness in the impact zone is set to a level to permit high forces to be transmitted. A large thickness would effectively soften the material and reduce the peak force. However, the thickness cannot be less than a level needed to prevent fracture.

The geometry of the cap is further shown by the cross section on Fig 4. The relative position of the hammer head impact face and the polymer insert are shown. Small interior protrusions on the cap can be added to insure a snug fit. Fig. 9. A small gap between the polymer insert as a cap and the hammer face side can be included as shown in Fig. 9, to accommodate slight variations of dimensions and still insure a snug fit.

The properties of the polymer cap must be set to compromise between two conflicting requirements. The polymer modulus must be high to insure a high peak impact force, and, the polymer's impact resistance must also be high. The difficulty in the prior art, which this invention addresses, arises because a low modulus is generally needed to achieve high impact resistance.

The preferred method of manufacture is to heat the retaining sleeve and expand it, slide the ring by the polymer insert, and onto the hammer head, leaving a protrusion of the polymer insert in the preferred mode of less than .020 inches. The polymer insert in this mode should have a larger area than the area of the impact face, and should be about .001 in. larger ( normally in diameter) than the retaining sleeve, which sleeve corresponds to the perimeter of the impact face of the hammer so that the retaining sleeve applies compression on the polymer insert. The rounding of the edge of the polymer insert if desired could be .005 inches. The invention enables the minimization of polymer material, which for the quality and characteristics of the preferred mode saves expense. A cap made of polymeric material would be proposed to normally be about .2 inches thick between the impact face of the hammer and the item to be struck.

To overcome the problem of failure of a polymer insert, the inventors utilize materials with inherently high impact resistance such as nylon polymers but not limited to them. Then, the polymer modulus is used in conjunction with the cap geometry to set the deformation resistance "k" to a maximum level consistent with durability requirements. The value of "k" can be computed from the following:

(Equation 1) k = E A / 1

E = polymer modulus (lb/sq in) for the selected polymer material A = cross section area (sq in) [3-5] t = polymer thickness in impact zone (in) [2-5] k = deformation resistance (lb/in)

The specific values of the above parameters will depend on the hammer in question.

The polymer material is preferably made of a reinforced polymer. The reinforcement can consist of combinations of toughening materials, reinforcing fibers (e.g. fiberglass), or minerals. An example of such a reinforced polymer is Zytel® 8018 (DuPont - Engineering Polymers) or DuPont Corp. MINLON® reinforced nylon, including, for example, 11C40 and 12T. Materials for the cap include, but are not limited to, the polymer families of: polyamides, polyesters, polyurethanes, polyaramids, PEEK, PEECK, acrylics, phenolics, polycarbonates; and, they may be reinforced with short fibers, long fibers, fabrics, minerals, toughening agents, other polymers, metals, or other substances. As a general matter mineral reinforced nylon or glass fiber reinforced nylons seem preferable. A more comprehensive list of materials can be found in, McCarty et al, pending U.S. Appl. No. 10/625,149 filed as utility application on or about 7/21/2003 which is adopted by reference.

Referring to the preferred mode of a polymer insert shaped like a disk with a retaining ring or sleeve, the invention is made by heating the retaining ring to expand it. The retaining ring is pressed over the polymer insert disposed on the hammer impact face and thus pressed around the hammer face side until only a distance d protrudes (Fig. 4). The distance d is preferred to be at least .190 inches. The polymer insert and the retaining ring which functions as a rigid metal sleeve cooperate in a novel way to accomplish an unexpected effect. The impact of a hit on the polymer insert puts compressive load on the polymer insert whereupon the polymer insert attempts to expand radially. The retaining ring which is functioning as a sleeve on the polymer insert increases the polymer's "effective modulus" by a large factor

F = (p - l) / (2 * p² + p -l) Where p = polymer Poisson Ratio F = factor of effective polymer modulus increase

The sleeve has another cooperative effective of limiting crack growth and the failure of the polymer insert.

(See, Glancey, J.L. et al "A reinforced Polymer Hammer Cap For Eliminating Metal-to-Metal Contact and Reducing Hand-Transmitted Vibration", No. 065012, 2006 ASABE Annual International Mtg, Portland, OR, July 2006).

In reviewing the earlier Equation 1 , k=(E*A)/t, and applying Equation 2, part of the novelty of the invention is that the rigid metal sleeve or retaining ring creates a factor of effective polymer modulus increase F which when multiplied by the pre-existing E (that is the polymer modulus) results in a higher effective polymer modulus E'.

E'=F*E

Where F = factor of effective polymer modulus increase (as before)

E= polymer modulus (lb/sq in) for the selected polymer material (as before) Thus, the deformation resistance k is increased to k' :

k'=E'*A /t

Therefore, to achieve the preferred deformation resistance, "t," the polymer insert thickness can be thicker and thus more durable and effective than a like polymer insert disposed on the impact face without a retaining ring or sleeve. Normally, the inventors propose to use a polymer insert that would function desirably without a retaining ring or sleeve, and then use the retaining ring or sleeve to reinforce and stiffen the polymer insert by increasing the effective polymer modulus E'.

Thus, the containment of the polymer in the retaining ring or sleeve, or in an alternative mode, within a cavity within the hammer (Fig. 6), enables a surprising and disproportionate increase from the modulus of the raw polymer material in a sense of creating a higher effective modulus for a given thickness of material. That higher effective modulus, from a layperson's perspective, means the material is stiffer and more force transmitted through the polymer. In formal terms, the deformation resistance is higher for a given thickness of material. The design of this invention overcomes a problem, in the prior art of relative softness of material which is ergonomically and economically undesirable.

The Cox '832 and '384 hammer patents are significantly different because they contemplate movement of a metal cap, so there is metal to metal contact with the nail or object being driven, against a soft; material, and do not contemplate the moving cap being used to exert centripetal force on the soft polymer material contemplated in the '832 and '384 patents. These Cox patents are assigned to Vaughan and Bushnell Manufacturing Company of Hebron, Illinois, and a current Vaughan hammer embodies at least one of the disclosed modes in the Cox patents.

The polymer insert in the shape of a cap over the impact face and hammer face side as discussed next does not achieve this sleeve-enhanced modulus though it presents a number of advantages, primarily durability and modulus, and most importantly from a safety viewpoint: no risk of metal to metal contact, even form an indirect hit.

The mode of invention of a polymer insert in the shape of a cap over the impact face proposes to conform the cap to the shape of the hammer head. The polymer insert in the shape of a cap should have the exterior corner of the impact face rounded or beveled to roughly imitate a curve of greater than 0.125 inches or 3 mm. If the hammer has a pronounced crown, the cap needs to conform to the crown; otherwise, the preferred mode is to conform to the crown, but it is less significant. If the hammer crown is curved at its edge between the impact face of the hammer and the circumference of the hammer, the preferred mode is to conform the polymer cap and have a curve of greater than 0.125 inches or 3 mm on the exterior corner of the polymer insert. The polymer insert in the shape of a cap can be removeable and replaceable.

A mode for securing the polymer cap is to use protrusions in the cap circumferential to the hammer head. A protrusion, preferably in the center can be used on the back of the cap to fit in a corresponding cavity in the hammer face.

Another mode of invention is as follows: The polymer insert can be designed to be set in a cavity in the impact face of the hammer as shown in Figure 7. In this mode, the polymer insert should protrude less than .02 inches. The corners of the polymer insert away from the impact face of the hammer can be rounded to .005 inches radius. The wall of the cavity need only be thick enough to contain the polymer insert and not fail on impact of the insert. The wall of the cavity then functions much like the previously- described retaining ring or sleeve holding the polymer insert shaped like a disk.

The polymer cap or polymer insert surrounded by a retaining sleeve or ring present the advantage of being removeable. The polymer cap is removable by tapping off cap. The polymer insert is removeable by tapping off the retaining ring or sleeve using light impacts and a backing surface. The impact face, while normally round, can be polygonal in shape and the retaining ring or sleeve congruently shaped to the polygonal shape.

The polymer insert can be replaced and the retaining ring or sleeve hammered on by annular pressure normal to the circumference of the sleeve.

The polymer cap or cap with a protrusion to hold it in place, or with friction ridges, can be tapped back on over the head of the hammer.

As an alternative mode of invention, in addition to previously described hammer cap mounting methods (cap over hammer face, polymer insert shaped as disk and rigid sleeve) there is a third way to secure the cap. In this geometry, a protrusion of the polymer insert is placed in a recess or pocket in the hammer face. This recess is generally, but not necessarily, cylindrical. The polymer insert is pressed into the recess and optionally may be secured with the appropriate adhesive. The inventors have discovered that by applying a cyclic compression force to the polymer insert to seat it, a surprising result has emerged of significantly improved reduction of time to failure. This compression and seating can be performed by utilizing an Instron (Boston, Mass.) hydraulic machine and applying a 40 Hz non-impacting pressure to the cap to seat it in a cavity in the interchangeable working tool. The polymer insert would be pressed snugly into the just described recess or cavity on the impact face of the hammer. The polymer insert, or protrusion from the polymer insert is loaded in by hydraulic compression for a number of cycles in order to fully insure that the polymer insert is fully compressed in the recess. This is referred to as cyclic compression load. An aperture can be included to enable better seating..

EXPERIMENTS Series I of experiments Experiment 1 - Basic Functionality Demonstration

This experiment was conducted to see if nails could be hammered into wood with a polymer sample placed between the hammer head and the nail.

Material Zytel® ST801 — (toughened nylon polymer DuPont -

Engineering Polymers) with retaining sleeve Polymer thickness .190 inches

Test 1 Hammer 3 inch standard nails through 1x2 inch pine Results: Done repeatedly (4 times) on same sample, no polymer damage, some surface discoloration. Approximately the same number of hammer blows as without polymer.

Test 2 Hammer out 3 inch nails previously driven through wood through 1 inch thick pine and protruding from back face

Results: Done repeatedly (4 times) on same sample, no polymer damage, roughening of surface. Approx same number of hammer blows as required without polymer.

Experiment 2 - Hammering Tests with Various Materials

This experiment was conducted to evaluate the functionality (nail driving) and durability of polymer inserts shaped as caps on a hammer. In order for the caps to match the hammer impact face contour, the face was ground flat. (An alternate way of matching contour is to shape the polymer insert shaped as a cap to match the conventional chamfer and crown of a hammer.) Materials

Wood: (2x4 pine) 1.5 inches thick

Nails: 3.5" standard, 2.5" standard, 2.5" finishing nail

Cap Thickness .250 inch (in impact zone)

Procedure

Nail was driven flat with wood surface (and protruding from back face) Each cap was inspected for damage AU caps tested made of DuPont polymers of varying types

Series II of experiments

Test Methods and Terminology

Nail Driving Efficiency

A standard test was developed to assess the ability of polymer faced hammers to drive nails. This basic test is obviously needed to demonstrate the functionality of a particular design and of a particular polymer type. The test was done using an automated hammer tester (ref- Glancey, JX. et al, "A New Cyclic Impact Device and Standard Testing Methodology for Hand Struck Tools:, No. IMECE2003-41455, Proc of 2003 ASME International Annual Meeting, Washington, DC). The test parameters on this tester were set to drive nails into wood.

Test conditions:

Polymer Faced Hammer - hammer with a polymer insert

Control Hammer — a conventional steel driving hammer with the same mass as the polymer faced hammer.

Impact Method -automated hammer tester

Impact Velocity - 5 meters per second

Wood - 100x100 mm treated wood post

Nail - 16 penny Test Procedure:

Preset nails into wood to depth of 12 mm

Measure change in Penetration Depth after 4 blows - hammer

Perform 10 replicates and compute the average penetration depth

Report results:

Nail Driving Efficiency = Average of Penetration Depth (polymer faced hammer) /

Average Penetration Depth (control hammer without polymer)

Accelerated Durability Rating

A standard test was developed to assess the ability of capped hammers to withstand repeated blows. The test was done using an automated hammer tester (ref — Glancey,J.L. et al, "A New Cyclic Impact Device and Standard Testing Methodology for Hand Struck Tools:, No. IMECE2003-41455, Proc of 2003 ASME International Annual Meeting, Washington, DC). The test parameters on this tester were set to harsh conditions in an "accelerated durability rating" test to simulate extended use.

Accelerated Durability Rating Test Conditions:

Impact velocity =18 ft./sec.=5.486 m/sec.

Impact Frequency = 1 Hz

Impact Target = Steel rod (Diameter=8 mm, Length=75mm) rigidly mounted. The rod has approximately the same diameter as the head of a 16 penny nail head nail head and cannot move

Impact Location on polymer insert face: All hits are offset from center by approximately

1/3 of the radius of the polymer insert face (for this testing approximately 10 mm offset), and all impacts on same spot are on polymer insert on hammer

Test Procedure:

Run impacts until steel rod penetrates lmm into polymer insert (terminate test at 500 cycles if less than lmm of penetration occurs). Polymer insert failure defined as lmm of permanent indentation occurring in less than 500 cycles.

Measure number of blows to failure (or no failure at 500 cycles) Report results: Accelerated Durability Rating = Number of cycles to failure in this test

Test Results - Series II

A number of polymer faced hammers were tested in controlled tests to assess performance. The results showed a surprising ability of hammers with polymer inserts and a retaining sleeve or ring as described in this invention to drive nails and also to survive a harsh test referred to as an "accelerated durability test." This performance has not previously been achieved with hammers in which a polymer is positioned between the hammer face and the surface to be impacted. (Measurement techniques are described in: Glancey, J.L. et al "A reinforced Polymer Hammer Cap For Eliminating Metal-to- Metal Contact and Reducing Hand-Transmitted Vibration", No. 065012, 2006 ASABE Annual International Mtg, Portland, OR, July 2006).

Experiment I - Nail Driving Efficiency of various hammers with polymer insert (Procedure defined above)

Base Polymer Type Depth After 4 Blows (mm) Nail Driving Efficiency

Range Average depth

Control Hammer - no polymer 38.7 to 45.0 41.7 100

Nylon Zytel® ST801 35.5 to 45.2 41.7 100

Polyester Crastin® ST820 37.1 to 44.7 40.9 98

Nylon Minion® 12T 35.9 to 45.8 41.1 99

Nylon Minion® 11 C40 36.7 to 46.8 41.1 99 Nylon Zytel® 8018 38.6 to 44.2 41.0 98

Vaughn Capped Hammer 35.7 to 42.0 39.4 92

(Model SH175)

Experiment II - Accelerated Durability Rating of various hammers with polymer insert

Base Polymer DuPont Type Accelerated Durability Rating

(cycles to failure)

Nylon Zytel® ST801 5

Polyester Crastin® ST820 4

Nylon Minion® 12T 27

Nylon Minion® 11 C40 >500

Nylon Zytel® 8018 38

Vaughn Capped Hammer (Model SH 175) 1

Experiment III —Hammer Vibration-retaining sleeve surrounding insert in various hammers with polymer insert

Base Polymer DuPont Type Measured Average Weighted Vibration

(m/sec²)

Control Hammer (no polymer) 9.5

Nylon Minion® 11 C40 5.5

Nylon Zytel® 8018 5.4

Experiment IV -Hammer Noise retaining sleeve surrounding polymer insert

A. User Rating of Sound Emission

Base Polymer DuPont Type Avg. Qualitative Noise Rating (O to 5 scale)

Control (no polymer) 3.3

Hammer

Nylon Minion® 11 C40 2.1

Nylon Zytel® 8018 2.0

B. Measured Sound Emission

Base Polymer DuPont Type Average Frequency Weighted Sound Level (dBA)

Control Hammer (no polymer) 103.9

Nylon Minion® 11C40 102.7

A hammer made according to the invention with a retaining ring or sleeve around a polymer insert set on the impact face of the hammer, as in Figure 4, can be expected to perform in a superior fashion to the hammer capped with polymer insert configured as cap over impact face and at least part of hammer face side, see Figure 5.

A hammer made according to the invention with a polymer insert in a cavity in the impact face of the hammer as illustrated in Figure 7 will have similar performance characteristics to a hammer made according to the invention with a retaining sleeve over a polymer insert set on the impact face of the hammer, as in Figure 4, both of which can be expected to conform in superior fashion to the hammer in Figure 5.

The term snap-in geometry is meant to include ridges or the like that fit to a series of concentric perturbations in the surface of the hammer on the sides roughly perpendicular to the impact face so that the hammer cap is essentially non-removable.

A mechanical connection is meant to mean screws, pins, adhesive or snap-in geometry elements sometimes referred to as interference elements which impede movement as between the polymer insert, which can be a cap or face, and the hammer head. The interference elements can be a tab or vertical indentation or annular ring around the hammer head on the hammer face side for a polymer insert shaped like a cap, or a tab, vertical indentation or annular ring located inside a cavity in the impact face for an insert inserted into the cavity. Also, the term mechanical connector means that one part to have another part placed on it is slightly larger so that the part placed in juxtaposition is held in place by compression, or if one part is to have another part placed within it, the part to be inserted is slightly larger.

An adhesive can be used to secure a polymer insert.

The placement of a radius on the polymer insert or polymer insert shaped as a cap reduces the tendency to mar on an off center hit such as hitting a nail slightly off center as it is almost completely driven.

The handle may also be cushioned by materials and technology in the art such as rubber, or various synthetic materials to further dissipate vibration. That (those) material(s) to cushion the handle are referred to as cushioning material.

The invention is not meant to be limited to the disclosures, including best mode of invention herein, and contemplates all equivalents to the invention and similar embodiments to the invention.

Claims

1. A hammer comprising: a hammer head attached to a handle, said hammer head having an impact end, said impact end having an impact face, said impact face further having at least one hammer face side aligned approximately perpendicularly to said face; said impact face having a juxtaposed polymer insert made of polymeric material in order to eliminate metal-to-metal contact to diminish noise, metal-to-metal contact and vibration; said hammer having a nail driving efficiency greater than 95% and said hammer having an accelerated durability rating greater than 20 cycles to failure.

2. The hammer according to claim 1 , further comprising: said polymeric material having a resulting higher modulus by the inclusion of an additive selected from the group of fiber, mineral or toughener.

3. The hammer according to claim 2, further comprising: said polymeric material being reinforced nylon.

4. The hammer according to claim 3, further comprising: said polymeric material being fiber reinforced nylon.

5. The hammer according to claim 3, further comprising: said polymeric material being mineral reinforced nylon.

6. The hammer according to claim 1 , further comprising: said polymeric material being reinforced by material selected from the group of mineral particulates.

7. The hammer according to claim 8, further comprising: said polymeric material being reinforced nylon.

8. The hammer according to claim 9, further comprising: said polymeric material being selected from the group of DuPont Corp. MINLON® mineral reinforced nylons.

9. The hammer according to claim 1, further comprising: said polymer insert being shaped as a cap over said impact face and said impact face having exterior edges rounded to not less than 0.125 in. radius.

10. The hammer according to claim 9, further comprising: said polymeric material having a resulting higher modulus by the inclusion of an additive selected from the group of fiber, mineral or toughener.

11. The hammer according to claim 10, further comprising: said polymeric material being reinforced nylon.

12. The hammer according to claim 11, further comprising: said polymeric material being fiber reinforced nylon.

13. The hammer according to claim 11, further comprising: said polymeric material being mineral reinforced nylon.

14. The hammer according to claim 9, further comprising: said polymeric material being reinforced by material selected from the group of mineral particulates.

15. The hammer according to claim 14, further comprising: said polymeric material being reinforced nylon.

16. The hammer according to claim 15, further comprising: said polymeric material being selected from the group of DuPont Corp. MINLON® mineral reinforced nylons.

17. The hammer according to claims 1-16, further comprising: a mechanical connection.

18. The hammer according to claims 1-16, further comprising: a retaining sleeve surrounding said polymer insert securing said polymer insert to said hammer head.

19. The hammer according to claims 1-16, further comprising: a retaining sleeve surrounding said polymer insert securing said polymer insert to said hammer head; and a mechanical connection.

20. The hammer according to claims 1-16, further comprising: said handle having cushioning material.

21. A hammer comprising: a hammer head attached to a handle, said hammer head having an impact end, said impact end having an impact face, said impact face further having at least one hammer face side aligned approximately perpendicularly to said face; said impact face having a juxtaposed polymer insert made of polymeric material in order to eliminate metal-to-metal contact to diminish noise, metal-to-metal contact and vibration; said polymeric material having a resulting higher modulus by the inclusion of an additive selected from the group of fiber, mineral or toughener; a removable retaining sleeve for securing said polymer insert to said impact face.

22. The hammer according to claim 21, further comprising: said polymeric material being reinforced nylon.

23. The hammer according to claim 22, further comprising: said polymeric material being mineral reinforced nylon.

24. The hammer according to claim 21, further comprising: said polymeric material being reinforced by material selected from the group of mineral particulates.

25. The hammer according to claim 25, further comprising: said polymeric material being reinforced nylon.

26. The hammer according to claim 26, further comprising: said polymeric material being selected from the group of DuPont Corp. MINLON® mineral reinforced nylons.

27. The hammer according to claim 21, further comprising: said polymer insert having exterior edges rounded to not less than 0.02 in. radius said hammer having a nail driving efficiency greater than 95%; and said hammer having an accelerated durability rating greater than 20 cycles to failure.

28. The hammer according to claim 27, further comprising: said polymeric material being reinforced by at least one material selected from the group of fiber, mineral or toughener.

29. The hammer according to claim 28, further comprising: said polymeric material being fiber reinforced nylon.

30. The hammer according to claim 28, further comprising: said polymeric material being mineral reinforced nylon.

31. The hammer according to claim 27, further comprising: said polymeric material being reinforced by material selected from the group of mineral particulates.

32. The hammer according to claim 31, further comprising: said polymeric material being reinforced nylon.

33. The hammer according to claim 32, further comprising: said polymeric material being selected from the group of DuPont Corp. MINLON® mineral reinforced nylons.

34. The hammer according to claims 21-33, further comprising: a mechanical connection.

35. The hammer according to claims 21-33, further comprising: said handle having cushioning material.

36. A hammer comprising: a hammer head attached to a handle, said hammer head having an impact end, said impact end having an impact face, said impact face further having at least one hammer face side aligned approximately perpendicularly to said face; said impact face having an exterior edge at the intersection of said at least one hammer face and said impact face; said impact face having cavity in said impact face surrounded by said at least one hammer face side; a polymer insert seated in said cavity made of polymeric material to diminish noise, metal-to-metal contact and vibration; said hammer having a nail driving efficiency greater than 95% and said hammer having an accelerated durability rating greater than 20 cycles to failure.

37. The hammer according to claim 36, further comprising: said polymeric material having a resulting higher modulus by the inclusion of an additive selected from the group of fiber, mineral or toughener.

38. The hammer according to claim 37, further comprising: said polymeric material being reinforced nylon.

39. The hammer according to claim 38, further comprising: said polymeric material being mineral reinforced nylon.

40. The hammer according to claim 39, further comprising: said polymeric material being selected from the group of DuPont Corp. MINLON® mineral reinforced nylons.

41. The hammer according to claim 36, further comprising: said polymer insert having an aperture to enable said polymer insert to be more deeply seated in said cavity.

42. The hammer according to claim 36, further comprising: said polymer insert having a lateral protrusion parallel to said impact face toward said exterior edge; said impact face adjacent to said cavity having an edge rounded to not less than .02 in. radius and said polymer insert having an interior corner conforming to said impact face having said exterior edges.

43. The hammer according to claim 42, further comprising: said polymeric material having a resulting higher modulus by the inclusion of an additive selected from the group of fiber, mineral or toughener.

44. The hammer according to claim 43, further comprising: said polymeric material being reinforced nylon.

45. The hammer according to claim 44, further comprising: said polymeric material being mineral reinforced nylon.

46. The hammer according to claim 45, further comprising: said polymeric material being selected from the group of DuPont Corp. MINLON® mineral reinforced nylons.

47. The hammer according to claim 42, further comprising: said protrusion and said polymer face cap having an aperture to enable said protrusion to be more deeply seated in said cavity.

48. The hammer according to claims 36-47, further comprising: a mechanical connection.

49. The hammer according to claims 36-47, further comprising: a retaining sleeve surrounding said polymer insert securing said polymer insert to said hammer head.

50. The hammer according to claims 36-47, further comprising: a retaining sleeve surrounding said polymer insert securing said polymer insert to said hammer head; and a mechanical connection.

51. A hammer comprising: a hammer head attached to a handle, said hammer head having an impact end, said impact end having an impact face, said impact face further having at least one hammer face side aligned approximately perpendicularly to said face; said impact face having a juxtaposed polymer insert made of polymeric material in order to eliminate metal-to-metal contact to diminish noise, metal-to-metal contact and vibration; said polymeric material being mineral reinforced nylon; said polymer insert having exterior edges rounded to not less than 0.005 in. radius; a removable retaining sleeve for securing said polymer insert to said impact face and containing expansion of said polymer insert in order to reinforce said polymer insert; and said exterior edge of said polymer insert not being exposed more than .02 inches beyond said removable retaining sleeve.

52. The hammer according to claim 51, further comprising: a mechanical connection.

53. The hammer according to claim 51, further comprising: said handle having cushioning material.

54. The hammer according to claim 51, further comprising: said polymeric material being selected from the group of DuPont Corp. MINLON® mineral reinforced nylons.

55. The hammer according to claim 52, further comprising: a mechanical connection.

56. The hammer according to claim 52, further comprising: said handle having cushioning material.

57. A method of manufacturing a hammer, said hammer having a hammer head attached to a handle, said hammer head having an impact end having an impact face, said impact face further having at least one hammer face side aligned approximately perpendicularly to said face, comprising the following steps: enabling the juxtaposition of a polymer face cap made of polymeric material to said impact face, said polymeric material being reinforced nylon, and said polymeric material being at least 0.001 in. larger in cross-section than the cross section of the perimeter around said impact face in order to diminish noise, vibration and spark, and to eliminate metal-to-metal contact upon direct hits by said hammer; heating a removable retaining sleeve shaped like the perimeter of said impact face, sliding said removable retaining sleeve by the perimeter of said polymer face cap onto said at least one hammer face side so as to enable a friction fit around said at least one hammer face side, and to enable a compression fit around said polymer face cap; and said sliding of said removable retaining sleeve being stopped when there is a protrusion of not less than 0.005 in. of said polymer face cap exterior to said retaining sleeve.