US3844321A

US3844321A - Unitarily cast hammer

Info

Publication number: US3844321A
Application number: US00357694A
Authority: US
Inventors: W Cook
Original assignee: Custom Electronic Systems Inc
Current assignee: Custom Electronic Systems Inc
Priority date: 1971-06-22
Filing date: 1973-05-07
Publication date: 1974-10-29
Anticipated expiration: 1991-10-29

Abstract

An impact tool in which a specifically configured skeletal stiffener is completely and unitarily encased in a thick resilient encasement. The part of the skeletal stiffener which forms the basis for the striking head of the tool may be internally provided with operatively movable and treated particles to inhibit any recoil of the head when an object is struck.

Description

C Umted States Patent [111 5,844,521

Cook Oct. 29, 1974 [54] UNlTARlLY CAST HAMMER 917,840 4/1909 Bird 145/29 R 2,604,914 7/1952 K hlen 145/29 B [75] Invent IndlanaPohs, 2,894,550 7/1959 cia 145/36 [73] Assignee: Custom Electronic Systems, Inc. 3,326,861 6/1967 Sandridge 260/75 lndlanapolls, Ind. FOREIGN PATENTS OR APPLICATIONS [22] Filed: May 7, 1973 225,938 2/1959 Australia 145/29 B 98,736 4/1940 Sweden 145/61 M [21] Appl. No.2 357,694

Related US Application Data Primary Examiner-A1 Lawrence Smith Assistant Examiner-.1. T. Zatarga [63] fgiltlnuation In part of Ser. No. 155,516, June 22, Attorney g or Firm-Trask, Jenkins & Hanley 52 U.S. Cl. 145/29 R, 145/29 B, 145/36 [57] ABSTRACT [51] Int. Cl B25d 1/00 An impact tool in which a specifically configured skel- [58] Field of Search 145/29 R, 29 A, 29 B, 29 C, etal stiffener is completely and unitarily encased in a 145/29 D, 36, 61 R, 61 A, 61 C, 61 D, 61 F, thick resilient encasement. The part of the skeletal 61 H, 61 K, 61 M stiffener which forms the basis for the striking head of the tool may be internally provided with operatively [56] References Cited movable and treated particles to inhibit any recoil of UNITED STATES PATENTS the head when an object is struck. 52,696 2/1866 Eddy 145/36 8 Claims, 6 Drawing Figures L l A SHEET 10F 2 PATEN'TED BET 2 9 I974 Fig.3

PATENTEDHBIZQ m4 7 sum 2 or 2 Fig.6

UNITARILY CAST HAMMER This is a continuation-in-part of my co-pending application Ser. No. 155,516, filed June 22, I971.

BACKGROUND OF THE INVENTION Impact tools such as hammers are well known in industrial environments. The uses for such tools are, in some instances, extremely specialized. A multiplicity of hammer constructions have been proposed to meet the majority of these specialized uses. For example, in the metal working industry, an impact tool is needed which does not mar the surfaces with which it comes in contact. Such a requirement propagated the use of hammer heads with Babbitt or lead composition. These hammers are satisfactory for forcing large machine parts into place, but due to their soft and malleable composition, are extremely short lived. They have the further disadvantage in that small pieces of the head material can be torn from the impact surface of the head during use which can affect the hydraulic valving of automated machine tools and the like in the vicinity in which the hammer is used. Thirdly, such hammers are usually not well balanced which, during prolonged use, causes undue fatique to the user.

Other hammer materials which have been selected for their non-marring properties, e.g., rubber, nylon or rawhide, also have extremely short lives thereby making their use economically impractical for any industry requiring large quantities of hammers.

There has also been a need for hammers and like impact tools in environments wherea no-sparking" type of flame protection is crucial. Accordingly, hammers have been proposed which utilize components of rubber, nylon or wood to give the required no spark characteristics. However, hammers made of these materials are difficult to manufacture without some type of metal fastener or wedge to hold them together and for the most part are not spark free and are again susceptible of relatively short working lives."

Therefore, the enviroment in which a hammer is to be used imposes certain critical restrictions upon the particular hammer which is utilized therein. The relatively wide variance in these restrictions can result in forcing a single industrial user to purchase many different types and makes of hammers if his specific uses are critical, yet divergent in nature.

It is, therefore, an object of this invention to provide a hammer which may be used in a plurality of restrictive environments; which is capable of an extremely long working life; and whose use does not result in undue fatique.

SUMMARY OF THE INVENTION This invention relates to a hammer that is extremely durable and is susceptible for use in a wide variety of situations and environments. The hammer can comprise a specifically configured skeletal member upon which a resilient impact encasement is unitarily molded or formed. Preferably, this escasement, which completely surrounds the skeleton, is comprised of an elastomeric material which is preferably a urethane composition.

The specifically configured skeletalmember, in general, includes a handle member which, at one end,'is centrally integral with or affixed .to a short tubular head member. The handle member can be provided with mechanical locking means to ensure that the overall hammer handle will not twist with respect to the hammer head during use. The tubular head member can be substantially filled with specifically treated lead particles, or the like, to yield a hammer which has little or no impact recoil. The ends of the filled head member are sealed with specifically configured end caps which contain the treated particles therein and operatively interact with the primary impact surfaces of the hammer to improve their striking characteristics.

The elastomeric encasement enables any part of the hammer to be used for striking another object without marring the surface of that object while the particle filled head gives the hammer striking weight and nonrecoil properties. Furthermore, the hammer will not spark upon impact with any material, thereby making it safe to be used under flammable conditions.

The unitarily formed encasement permits the head and handle of the hammer to be effectively formed as one piece, thereby allowing close control of the balance characteristics of the hammer. The effective one piece construction also eliminates the possiblity of any separation of the head and handle of the hammer during use. The hammer hardness or durometer of the impact receiving encasement can be altered while maintaining the balanced characteristic of the hammer by altering the composition of the elastomeric material.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate the invention and, by way of example, show a preferred embodiment. In such drawings:

FIG. 1 shows one embodiment of the invention, taken in partial section;

FIG. 2 is a sectional view of the hammer shown in FIG. 1;

FIG. 3 is a sectional view taken along line 33 of FIG. 2;

FIG. 4 shows a mold used in making the hammer of FIG. 1;

FIG. 5 is a perspective showing of an alternate embodiment of the skeletal insert utilized in the invention; and

FIG. 6 is a side view, taken in section, of a mold for a hammer using the skeletal insert of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A hammer embodying one form of the invention is shown in FIGS. 1 and 2 and generally comprises a specifically configured skeletal portion 10 about which a thick resilient encasement 12 is unitarily cast. The encasement is preferably formed from an elastomeric material such as of a urethane composition. Urethane has been found to have qualities which render it advantageous for use in the preferred embodiment of the invention. It has been found to be extremely durable and is controllably resilient. Furthermore, urethane will not support a flame nor will it spark on contact with any other substance.

The impact hardness of the resilient encasement 12, when formed from urethane, is controllable by altering the amount of a hardener, such as isocyanate, which is added during the composition of the urethane material and while it is still in a liquid state. It should be noted that the complete encasement of the specifically configured skeletal insert 10 permits the hammer to be struck anywhere on its surface area without generating a spark or damaging the surface finish of the object which is struck.

The specific construction of the skeletal insert is best shown in FIGS. 2 and 3. The insert 10 is, in general, comprised of a short tubular head member I4 which is symmetrically disposed within the head portion 16 of the hammer encasement 12. A handle member 18 is formed by wrapping a relatively narrow strip of steel or like material around the tubular head member 14. and subsequently fastening the two extending and

mating strips

20 and 22 together as by welding. It has been found sufficient to weld the

strips

20 and 22 at their juncture 24 next to the head member 14 and at the ends 26 of the strips. The planar surfaces of the

handle strips

20 and 22 have been found to provide a so-called mechanical locking of the encasement 12 about the strips to eliminate any twisting of the handle with respect to the head during heavy use.

It should be noted that the impact forces which the hammer will primarily receive will be in the axial direction of the tubular head member. Such forces will subsequently be transmitted to the

handle strips

20 and 22 in a plane parallel to the surface of the strips and against their edges. The disposition of the

handle strips

20 and 22 with respect to the head member 14 thereby gives the hammer a great amount of unyielding strength in the impact direction.

In the preferred embodiment, it has been found desirable to interpose two locating and supporting

members

28 and 30 between the two

handle strips

20 and 22 prior to welding them together. Preferably, these locating

members

28 and 30 extend perpendicularly from between the handle strips 20 and 22 and are used, as will be explained in detail below, to locate and support the entire skeletal insert 10 within a mold. The

members

28 and 30 are preferably comprised of an identical material to that which will'later form the resilient encasement 12 around the skeletal insert 10. After molding, these locating members can be trimmed flush with the exterior surface of the encasement 12.

The tubular head member 14 can be substantially filled with small, lead shot 32 to give the hammer added striking weight and to retard any impact recoil of the head 16 after striking an object. It has been found that excellent and longlived recoil retardation is obtained by treating the lead shot 32 with a silicone liquid prior to its insertion in the head member 14. It is believed that the silicon film imposed on the surfaces of the lead shot reduces the friction therebetween to substantially aid the non-recoil characteristics of the hammer. The frictional reduction has also been found to reduce the resultant heat which is built up inside the tubular head member 14. Conventionally, this heat build-up, particularly occurring in the larger sized hammers during prolonged and strenuous use, has actually resulted in the melting of the individual lead shot such that a single, unitary ball" of lead results which makes the nonrecoil characteristics of the hammer inoperable.

In practice, one end of the tubular head member 14 is first sealed by a specific cap 34 prior to adding the lead shot 32. After the shot 32 has been inserted, the opposite end of the tubular head member 14 is similarly supplied with a cap 34. These caps 34 are specially configured to aid the longevity and striking capabilities of the hammer. More specifically, the circumferential edges of the caps 34 are rounded to evenly disperse the striking force transmitted to these edges when the primary striking surfaces 36 of the hammer strike an object. Secondly, it has been found extremely advantageous to make the caps 34 concave in nature to provide operative interaction with the slightly convex or crowned exterior surface of the primary striking areas 36. As an object is struck, the outer, crowned surface 36 deflects inwardly, and such deflection is transmitted through the encasement to the particular cap 34. The concave surface of the cap 34 permits this inward and transmitted deflection to continue for a short distance instead of causing a reaction against such deflection which could cause the hammer to ricochet off of the struck object. In other words, the concave surface of the caps 34 permits the flattening of the convex impact surface 36 before the cap effectively reacts against the inward force thereby ensuring an effective flat and even striking of the external surface 36 of the hammer head 16 without ricocheting.

As previously mentioned, the locating and supporting

members

28 and 30 which are compressibly disposed between the handle strips 20 and 22 of the insert 10 are used to support the insert 10 during the molding of the resilient encasement 12. With reference to FIG. 4, the skeletal insert 10 containing the supporting

members

28 and 30 is placed in a female half mold 38 and supported therein by the supporting

members

28 and 30 which are received in

slots

40 and 42 formed in the mold. The other half of the mold (not shown), which preferably contains locating pins, is then placed in opposing relationship with the first mold half 38. The pins (not shown) are received in locating pin holes 44 in the first mold half 38 for precisely locating and maintaining the relationship between the two mold halves. The outer surface of the mold halves 38 can be provided with flat portions 46 for receiving clamps (not shown) for clamping the two mold halves together.

The mold halves 38 are provided with a so-called pour hole 47 into which is poured, in the preferred embodiment, a liquid urethane composition. The urethane flows down into the mold 38 and around the insert 10 to form what will be the resilient encasement 12.

The filled molds containing the insert 10 and the liquid urethane composition, are then subjected to an elevated temperature within a setting oven for approximately 20 minutes after which the mold halves 38 are separated and the resulting hammer removed. The supporting

members

28 and 30 are then trimmed, along with any excess material in the pour hole 47, to be flush with the exterior of the handle of the completed hammer to complete the main formation process. Subsequently thereto, the hammers are cured at a second elevated temperature for a number of hours to complete the formation.

The urethane composition has been found to be an excellent material from which to make the resilient encasement 12 used in the invention. It has been found, from extensive testing of the invention, to have an extremely long working life. The hardness, or durometer, of the resultant hammer can be controllably adjusted by the addition or elimination of a portion of a hardener, such as isocyanate, which is added to the urethane to form the composition which is poured into the mold halves 38.

An alternate embodiment of the skeletal insert 10 is shown in FIG. 5. In this insert 48, the handle member 50 is formed from a small diameter steel rod, tube or the like. Again, the head portion of the insert 48 is formed from a tubular member 52 which preferably contains a significant amount of silicon treated lead shot, or the like. The ends of the tubular head member 52 are sealed by caps 54 which, like the caps shown in FIGS. 1 through 3, are rounded at the edges and are axially concave.

In this embodiment, however, the handle rod or tube member 50 passes through the tubular head member 52 and is welded or otherwise secured to the tubular head member 52 at its exit point 56. If desired, the handle 50 can also be welded to the head member 52 at its entrance point 58.

A mechanical locking strip 60 is secured, as by welding, to the handle member 50. The mechanical locking strip 60, which is formed from steel or a similar material, has been found advantageous in that when the resilient encasement 16 is formed therearound, the planar surfaces of the strip 60 serve to lock or otherwise prohibit any rotation of the hammer handle with respect to the head of the hammer during strenuous use.

A two-part mold for molding a resilient encasement about the insert 48 of FIG. 5 is illustrated in FIG. 6. instead of the supporting

members

28 and 30 as in the insert of FIG. 1 through 3, locating pins 62 through 64 are secured in the mold halves 66 and 68 and protrude therefrom. The handle member 50 is supplied with three spatially disposed holes 70 through 72 for securedly mounting the insert 48 thereon and precisely locating the insert 48 within the mold. As before, the mold halves 66 and 68 are then closed in mutually opposing relationship with such relationship being maintained as by pins 74.

After pouring the urethane composition into the mold and around the insert 48, the mold is placed for a sufficient time in the setting oven. The mold halves 66 and 68 are subsequently separated and the completed hammer is removed from the pins and cured. Preferably, the pins 62 through 64 are small enough in diameter to make the resultant holes in the resilient encasement imperceptible without close inspection, and, in any event, without detriment to the finished product.

I claim:

1. An impact tool, which comprises a skeletal insert member, said skeletal insert member including a tubular head member and a handle member secured to said tubular head member, and an elastomeric encasement, said skeletal insert member being completely encased in said elastomeric encasement, said handle member having mechanical locking means thereon for preventing any twisting of the handle of the impact tool with respect to the head of the impact tool.

2. An impact tool as claimed in claim 1, wherein said elastomeric encasement forms a handle portion for the impact tool about said handle member and a head portion for the impact tool about said tubular head member, said head portion having a plurality of convex primary striking surfaces, and concave end caps secured over the ends of said tubular head member for operatively interacting with said convex primary impact surface of said head portion as an object is struck by one of said primary striking surfaces of the impact tool.

3. An impact tool as claimed in claim 2 including an amount of treated particles movably disposed in said tubular head member andheld therein by said end caps, said treated particles being for operatively interacting with said end caps for preventing recoil of said head portion after an object is struck by said head portion.

4. An impact tool as claimed in claim 3 wherein said treated particles include an amount of shot which is treated with liquid silicone.

5. An impact tool as claimed in claim 1, wherein said skeletal handle member includes a planar strip of metal secured to said handle member to provide said mechanical locking means.

6. An impact tool as claimed in claim 1, wherein said handle member is comprised of a metal strip, said metal strip having a flat first handle portion, a portion around said tubular head member, and a flat second handle portion adjacent and fixed to said first handle portion, and wherein said first handle portion and said second handle portion having elastomeric locating and supporting means compressibly imposed therebetween for locating and supporting said skeletal insert member in a mold during the encasing of said skeletal insert in said elastomeric encasement.

7. An impact tool as claimed in claim 6 wherein said elastomeric encasement is comprised substantially of urethane.

8. An impact tool as claimed in cliam 2 wherein said skeletal handle member is circular in cross section and wherein said mechanical locking means includes a metal strip secured to said circular handle member.

Claims

3. An impact tool as claimed in claim 2 including an amount of treated particles movably disposed in said tubular head member and held therein by said end caps, said treated particles being for operatively interacting with said end caps for preventing recoil of said head portion after an object is struck by said head portion.