US3623247A

US3623247A - High strength digging tooth

Info

Publication number: US3623247A
Application number: US5806A
Authority: US
Inventors: Visvaldis A Stepe
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1970-01-26
Filing date: 1970-01-26
Publication date: 1971-11-30
Anticipated expiration: 1988-11-30
Also published as: BE761991A; CA920805A; DE2102923A1; FR2077010A5

Abstract

A REPLACEABLE TIP OF A DIGGING TOOTH FOR EARTHMOVING EQUIPMENT OR THE LIKE HAS A SOCKET CAVITY INTO WHICH A TOOTHLIKE SUPPORT IS RECEIVED, THE TIP BEING RETAINED ON THE SUPPORT BY A TRANSVERSE PIN. THE POSSIBILITY OF BREAKAGE OF THE TIP UNDER SEVERE LOAD FORCES IS REDUCED BY RECESSING CENTRAL PORTION OF THE CONTACTING SURFACES OF THE TIP OR SUPPORT MEANS WITHIN THE CAVITY THEREBY ASSURING THAT STRESSES ARE DIRECTED TO THE RELATIVELY HIGH STRENGTH SIDE REGIONS OF THE TIP.

Description

NOV. 30, 1971 v TEP 3,623,247

HIGH STRENGTH DIGGING TOOTH Filed Jan. 26, 1970 1 She0ts-Shoot l VISVALDIS A. STEPE fi r, & 7"? M 91% XIWDRNHYS NOV. 30, 1971 v STEPE 3,623,241

HIGH STRENGTH DIGGING TOOTH Filed Jan. 26, 1970 4 Sheets-Sheet 8 NOV. 30, 1971 v STEPE 3,623,247

HIGH STREN GGGGGGGGGGGGG TH Filed Jan. 26, 1970 4 Sheets-Shoot 5 INVf-INTOR VISVALPIS A. STEPE NOV. 30, 1971 v, STEPE 3,623,241

HIGH STRENGTH DIGGING TOOTH Filed Jan. 26, 1970 -1 Shoots-Shoot 4 INVI1'N'H )R VISVALDIS A. STEPE BY i v I J K L 53 56 W W 9 A'r-zmm-zw United States Patent 3,623,247 HIGH STRENGTH DIGGING TOOTH Visvaldis A. Stepe, Willow Spring, Ill., assignor to Caterpillar Tractor Co., Peoria, Ill. Filed Jan. 26, 1970, Ser. No. 5,806 Int. Cl. E02f 9/28 US. Cl. 37-142 R 1 Claim ABSTRACT OF THE DISCLOSURE A replaceable tip of a digging tooth for earthmoving equipment or the like has a socket cavity into which a toothlike support is received, the tip being retained on the support by a transverse pin. The possibility of breakage of the tip under severe load forces is reduced by recessing central portions of the contacting surfaces of the tip or support means within the cavity thereby assuring that stresses are directed to the relatively high strength side regions of the tip.

BACKGROUND OF THE INVENTION This invention relates to mechanical teeth carried on various forms of equipment for digging into earth or other material and more particularly to digging teeth having replaceable tips.

Powered earthworking equipment such as scrapers, loaders and rippers as well as apparatus for handling other material frequently have one or more digging teeth disposed along a cutting edge to loosen earth or other material. As considerable abrasion and impact damage may occur in use, the teeth usually have tips which may be removed and replaced. In most such constructions, the tip has a pointed forward end and has a socket cavity formed in the opposite end to receive a toothlike extension of an adapter or other support means and a transverse pin secures the tip to the adapter. To avoid the high cost of precision finishing, loose tolerances between the sidewalls of the tip and adapter are usually present. Clearance is also provided where the retainer pin transpierces the skirt of the tip and forward end of the adapter contacts the base of the socket so that load forces are transmitted directly between the tip and adapter rather than through the pin. As a consequence of this construction, a slight amount of rocking motion of the tip relative to the adapter may occur.

Thus, load forces on the tip tend to bend the tip relative to the adapter and this generates stresses within the skirt region of the tip which defines the socket cavity. If sufiiciently severe, such forces cause a catastrophic failure of the tip and such breakage is a fairly common occurrence in practice. This is highly undesirable, not only because of the cost of replacing the tips and possibly the adapter, but also because of the resulting delays in operation of the associated equipment. To decrease the fre quency of tip breakage, it has heretofore been thought necessary to use more costly higher strength tip material, or to increase the massiveness of the tip.

SUMMARY OF THE INVENTION 7 ating very high transverse bending moments in the skirt of the tip.

ice

Accordingly, it is an object of this invention to provide a digging tooth construction including a replaceable tip wherein tip breakage from external load forces is less likely to occur.

The invention, together with further objects and advantages thereof, will best be understood by reference to the following description of preferred embodiments in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a perspective view of a ripper tooth of a type to which the invention is applicable;

FIG. 2 is a cross-section view through a prior art digging tooth of the general type shown in FIG. 1 illustrating a structural characteristic of prior art tooth constructions which results in a proneness to breakage in the presence of severe load forces;

FIG. 3 is a side view of a digging tooth in accordance with the present invention with certain portions of the replaceable tip of the tooth being broken out;

FIG. 4 is a cross-section view of the tooth construction of FIG. 3 taken along the line IVIV thereof;

FIG. 5 is a fragmentary section view taken along line VV of FIG. 4;

FIG. 6 is a side view of a second embodiment of the invention with portions of the structure being broken out;

FIG. 7 is a cross-section view taken along line VIIVII of FIG. 6;

FIG. 8 is a broken out side view of a third embodiment of the invention;

FIG. 9 is a cross-section view of the digging tooth of FIG. 8 taken along line IXIX thereof, and

FIG. 10 is a fragmentary section view taken along lin X-X of FIG. 9.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawing, there is shown a digging tooth 10 of a general type employed on earthworking equipment and on apparatus for handling certain other forms of bulk materials as well. Teeth of this general type are used, for example, on the cutting edges of scrapers and loader buckets for the purpose of loosening earth or other material which is to be loaded. For purposes of illustration, the tooth 10 shown herein is of the form employed on the shank 11 of a ripper of the kind which is drawn behind a tractor to loosen earth, it being understood that the tooth construction is not limited to this particular usage.

A tooth 10 of this general type has a replaceable tip element 12 which may be of substantially rectangular cross-section, preferably with rounded edges, and is Wedge shaped to taper towards a linear edge 13 at the forward end. The support means for tip 12 is an adapter element 14 which in the present example is formed integrally on the lower forwardly extending portion of the ripper shank 11. In some other digging teeth, the adapter or support may be a separate element from the implement with which the tooth is used.

Adapter 14 has a configuration generally resembling that of the tip 12 but is of somewhat smaller dimensions, so that it may be received into a conforming socket cavity 16 in the back end of the tip, and the adapter has a relatively blunt forward end. Thus, the tip 12 is supported by adapter 14 and to retain the tip thereon a pin 17 may be transpierced through both elements in the region of the socket cavity. To assure that load forces are transferred 0 directly between the tip 12 and adapter 14, the passages Referring now to FIG. 2 in conjunction with FIG. 1, cost considerations generally prevent machining of the inner surfaces of cavity 16 and the outer surfaces of adapter 14 to the close tolerances which would be necessary to provide a precision fit. Thus, there are irregularities in the adjacent surfaces of the two elements, as shown in somewhat exaggerated form in FIG. 2, and a small clearance space of randomly variable magnitude is present between the adapter 14 and the skirt 19 of tip 12 within cavity 16. I have discovered that this clearance space and more particularly the irregularity thereof is a highly significant causative factor in tip breakage. In the presence of such random manufacturing variations, certain specific tips will have a chance configuration which is particularly prone to promote breakage.

In particular, a load force acting downward and backward on the forward end of tip 12 as indicated by arrow P in FIG. 1 creates sheer and tensile stresses at the back of the tip as is well recognized in the art but it has not heretofore been recognized that a transverse bending moment is also generated about the corners of the skirt as illustrated in FIG. 2. Due to manufacturing irregularities in the underside surface 21 of adapter 14 and the bottom surface 22 of socket cavity 16 load stress may be concentrated at certain points rather than being evenly distributed. Further, the primary point of contact P may randomly occur at any position along a transverse line through the tooth, the contact point being illustrated as being midway between the sidewalls of socket 16 in FIG. 2.

Thus, in the presence of a load force P on the tip of the tooth as shown in FIG. 1, a transverse bending moment exists at each bottom corner 23 of the skirt 19 wherein the magnitude of the bending moment at a particular corner 23 is proportional to the product of the stress force at point P and the distance L between point P and the corner 23. Comparative failure tests of conventional tips and tips embodying the present invention have demonstrated that these bending moments are a primary factor in tip breakage.

Having recognized the situation discussed above, it becomes possible to reduce the likelihood of tip breakage. While the total load forces at contact points P cannot be reduced without changing the socket to overall length ratio, it is possible to limit the size of the bending moments by controlling the location of the contact points P so that the moment arm L will necessarily be relatively small and the load P divided. This is accomplished by slightly recessing the area of surface 21 or surface 22, or both, at the more central portions thereof whereby the load is divided between at least two contact points P close to the corners 23 and 23' and therefore produce relatively low bending moments. Thus, the strength of the tooth can actually be increased by removing material.

A first example of a digging tooth embodying this higher strength construction is illustrated in FIGS. 3 to 5. Basic elements of the tooth 10' of FIGS. 3 to 5 may be essentially similar to that previously described except for the presence of recesses in certain surfaces as will hereinafter be discussed in more detail. Thus, the tooth has a tip 12' with a socket cavity 16 into which an adapter element 14' is received each element having the general configuration hereinbefore described. As in the previous instance, a retainer pin 17' transpierces both the tip 12' and adapter 14.

To limit bending moments of the kind discussed above, the bottom Surface 22' of socket cavity 16' is formed with a slightly recessed area 24 centered between bottom corners 23" and 23" of skirt 19' but which does not reach either corner. As best shown in FIG. 5 the recessed area 24 extends from about one-half of the depth of cavity 16 to the open back end thereof and is of progressively greater width towards the open end of the cavity.

Accordingly, as illustrated in FIG. 4, the transverse bending moments about corners 23" and 23" can have 4 only a relatively small effective moment arm L. The value of P in FIG. 4 has been decreased since the load force has been divided between the two corners. For a given load force on the tip 10' the bending moments tending to promote skirt breakage are greatly reduced without any increase in the size of the tooth or any change in the quality of the metal employed.

Since an upwardly directed load force on the point of the tip 10 can create essentially similar bending moments about the upper corners 26 and 26' of tip skirt 19, it is also advantageous to provide a similar recess 24' at the upper surface 27 of socket cavity 16. This provides for the beneficial load distribution if the tip is inverted.

Relief of loading on the rear central areas of the top and bottom of the tip skirt as described above can advantageously be combined with a further strengthening of the tip without necessitating an increase in overall size. Referring now to FIGS. 6 and 7, a second embodiment of the invention is shown which includes a tip 12" with socket cavity 16" into which an adapter 14 is received and having a transverse pin 17" for retaining the tip on the adapter as previously described. The central portions of the top and

bottom surfaces

28 and 29 respectively of socket cavity 16 as well as the central portions of the upper and lower surfaces 31 and 32 of adapter 14' are inclined with respect to each other as hereinbefore described and the back central portions 28 and 29' of the tip surfaces in this area are recessed as previously described so that contact is confined to the side regions of the surfaces to limit bending moments. The side regions of socket cavity surfaces 28 and 29 which border the recessed areasi.e., the contact zones, are angled relative to the rest of the

surfaces

28 and 29 so that additional material is present in the corners 33 of the skirt, with the corners being thickest at the back end of cavity 16". The side areas of adapter surfaces 31 and 32 are similarly angled relative to the central areas thereof to accommodate to the thickened corners 33 of the tip 12". To provide for including a maximum amount of material at the back of the tip corners 33, the side areas of surfaces 28 and 31 and the side areas of

surfaces

29 and 32 may be made parallel in the back region of the socket cavity 16". Accordingly, bending moments at the corners 33 of the tip 12" are limited to relatively low magnitudes and the thickness of the material in the critical corner regions is increased as well. This further increases tip strength and adds to wear life.

The increase in reliability of a digging tooth against breakage may also be realized by forming essentially similar recesses in the adapter element rather than the tip itself since this also confines stress to the side regions of the tip skirt. A tooth construction of this form is shown in FIGS. 8 to 10.

Referring now to FIGS. 8 to 10 in conjunction, tooth 10" again has a wedge shaped replaceable tip 36 with a socket cavity 37 for receiving a conforming adapter element 38 and the two components are transpierced by a retainer pin 39 which secures the tip on the adapter. As best seen in FIGS. 9 and 10 in particular, the tip 36 including the cavity 37 and skirt region 41 around the cavity may be of essentially conventional construction. Control of load forces to reduce bending moments about the corners 52 at the top and bottom of the skirt is provided by forming recesses 53 and 53- respectively in the top and

bottom surfaces

54 and 56 of adapter 38. As best seen in FIG. 10, the recesses 53, which may be of rectangular configuration in this embodiment, are confined to the intermediate region of

surfaces

54 and 56 and very importantly extend through the open end of tip socket cavity 37 a small distance when the tip is emplaced on adapter 38.

What is claimed is:

1. A digging tooth comprising:

support means having an adapter extension with opposite outer surfaces, the side regions of each of said outer surfaces being angled relative to the other portions of said outer surfaces, and

a replacable tip element disposed on said support means and having a socket cavity with an opening into which said adapter extension of said support means is received, said cavity having opposite inner surfaces which face said outer surfaces of said adapter extension, each of said inner surfaces of said tip element having a recessed area confined to an intermediate region between the side regions thereof, said recessed areas in said inner surfaces of said tip element being confined to the portions of said inner surfaces closest to said opening of said cavity and the regions of said inner surfaces on each side of said recessed areas being angled relative to the other portions of said inner surfaces to fit against angled side regions of said outer surfaces of said adapter extension with the portions of said tip adjacent said side regions of said inner surfaces being of progressively greater thickness towards said opening of said cavity.

References Cited UNITED STATES PATENTS 4/ 1970 Radwill 37142 R l/1960 Larsen 37-142 R 9/1959 Ratkowski 37 -142 R 5/1969 Hensley 37142 R 5/ 1961 Stephenson 37142 R 4/1969 Rhoads 37142 X 1/1960 Opsahl 37-142 R 9/1970 Steil 37142 R l/1941 Ratkowski 37142 R 4/1946 Askue 37142 R 3/1962 Brunner 37--142 A FOREIGN PATENTS France 37142 A US. Cl. X.R.