US3160967A

US3160967A - Removable blade arrangment with recesses therein for receiving support projections

Info

Publication number: US3160967A
Authority: US
Inventors: Irvin H Nichols
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-09-10
Filing date: 1963-09-10
Publication date: 1964-12-15
Anticipated expiration: 1981-12-15

Description

H. NICHOLS 3,160,967 REMOVABLE BLADE ARRANGEMENT WITH RECESSES THEREIN FOR RECEIVING SUPPORT PROJECTIONS Original Filed Aug. 7, 1961 2 Sheets-Sheet 1 Dec. 15, 1964 INVENTOR.

IRVIN H. NICHOLS ATTORNEY FIG. 2

Dec. 15, 1964 H. NICHOLS 3,160,967

REMOVABLE BLADE AR RANGEMENT WITH RECESSES THEREIN FOR RECEIVING SUPPORT PROJECTIO Original Filed Aug. '7, 1961 2 ets-Sheet 2 FIG.4 2 4 INVENTOR.

IRVIN H. NICHOLS FIG. 5

ATTORNEY United States Patent 3,160,967 REMGVAELE BLADE ANGEMENT WITH RECESSES THEREKN FUR RECEIVWG SUP- PORT PROXECTKGNS lrvin H. Nichols, 10192 Mclvlichael, Garden Grove, (lalif. Qontinuation of application Ser. No. 129,665, Aug. '7, 1961. This application Sept. 1963, Ser. No. 30?),3il3 22 Claims. (Cl. 37-441) This application is a continuation of my co-pending application for Removable Blade Arrangement, Serial No. 129,665, filed August 7, 1961 now abandoned.

This invention pertains to an arrangement for removably supporting blades utilized in earth moving equipment and the like.

The blades of earth movers, bulldozers, scrapers, and

similar equipment, although of rugged construction, are

unthreading and removal of these bolts, together with the nature of the blade connection, requires an expenditure of considerable time. Hence, blade removal and replacement not only is an inconvenience in view of the necessity of allowing the equipment to stand idle during the change, but it also is expensive in view of the amount of labor necessitated in effecting the replacement.

The present invention provides a removable blade arrangement drastically reducing the time required for both removal and attachment. This is achieved by means of a blade member having a receptacle in its inner end for receiving a projection portion of the equipment to which it is attached. Spaced flanges or other interconnecting elements throughout the receptacle portions give the unit added strength and assure that there will be no tendency toward separation at the inner end of the blade unit. Attachment to the equipment is effected by means of drive pins of resilient nature such that the pins hold the elements together in firm contacting relationship yet can readily be inserted or removed.

Accordingly, it is an object of this invention to provide a removable blade arrangement. requiring-a minimum amount of time for effecting an exchange of blade members.

Another object of this invention is to provide a blade unit readily removable, yet of high strength construction.

A further object of this invention is to provide an arrangement for holding a removable blade to adjacent structure with a firm, vibration-free connection.

Yet another object of this invention is to provide a blade attachment and removal arrangement requiring no special equipment or tools.

An additional object of this invention is to provide a resilient compressible drive pin for attaching a removableblade to adjacent structure.

- These and other objects will become apparent from the following detailed description taken in connection .with the accompanying drawing in which:

FIGURE 1 is a perspectiveview of the support and removable blade of this invention;

FIGURE 2 is a front elevational view of the inner edge of the blade;

FIGURE 3 is a top-plan view, partially broken away, showing the removable blade secured to the support member;

FIGURE 4 is an enlarged transverse sectional view taken along line 4-4 of FIGURE 3 illustrating the drive pin connection between the'blade and the support;

FIGURE 5 is a perspective view of the drive pin used in connecting the parts together; FIGURE 6 is a fragmentary sectional view illustrating the drive pin in a different rotational position from that of FIGURE 4 in connecting the removable blade to the support; and

FIGURE 7 is a fragmentary perspective View, partially in section, of a modified form of wear plate that does not use solid webs.

As illustrated in the drawing, the device of this invention is shown as applied to an earth mover, although it is equally usable with other forms of equipment where a blade or similar item is to be supported. The blade assembly 1 projects outwardly from mold board 2 of the earth mover, and includes a base support member 3 the inner end of which is substantially L-shaped and is welded to the mold board. The flange 4 of the member 3 bears against the end surface of the mold board and carries a wedge-shaped projection 5 extending from its central portion. The section 5 of the baseunit is adapted to hold removable wear plate 6. The latter member forms the blade for engaging the earth, and hence it too is substantially wedge-shaped with its

outer faces

7 and 8 being convergent outwardly.

A recess 9 extends into the inner edge 10 of the wear plate 6 and is adapted to receive the projection 5- of the base unit. Hence, the receptacle 9 is substantially complementary to the projecting member 5 so that when the inner edge 10 of the member 6 is adjacent the base flange 4 the projecting element 5 will be snugly received within the receptacle 9. Normally a clearance 11 will be provided at the end of member 5 to assure that the parts will fit together properly.

In order to assure that the outer blade element 6 is of adequate strength and will not tend to spread apart at its inner edge 10, there is included a plurality of spaced parallel webs 12. Each of these webs extends across the recess 9 and runs the width of the recess. These webs serve to tie together the two segments of the wear plate 6 at the location of the recess 9, thereby precluding any tendency for the blade to open up at its inner end during use. It is necessary to include slots 13 in the support 5 which substantially complementarily receive the webs when the parts are assembled.

The two portions of the blade assembly are held to gether by means of drive pins 14. These members may include a duality of

outside plates

15 and 16 interconnected by a bonded rubber lamina 17. The straight

upper sections

18 and 19 of the

outer plates

15 and 16 may be substantially parallel, as illustrated, connecting to rounded and slightly downwardly

inclined shoulders

20 and 21. The

bottom wall portions

22 and 23 of the pins are convergent'downwardly.

When the outer wear plate 6 is positioned on the base unit 3, aligned

openings

25 and 26 in the walls of the wear plate will be brought into registry with apertures 27 through the projecting element 5. The forward and

rearward walls

28 and 29 of the latter openings are convergent downwardly. At their upper ends the apertures 27 are of greater width than that of the lower edges of openings 25.

When the two components of the blade assembly have been thus positioned, the pins 14 are driven downwardly through openings 25 to enter also

openings

26 and 27. The convergence of the

lower Walls

22 and 23 permits the pins to enter the openings 25 readily. However, the upper portions of the walls Hand 23 are wider than the openings 25 resulting in a compression of resilient layer 17 as the pin is forced into the openings. However, as soon as the shoulders 2b and 21 pass the lower edges of the opening 25, the side sections and 16 are forced outwardly by the resilient element 17 bringing the shoulders underneath the edges of the opening 25.

This means that the pins 14 will serve to hold the parts together and will not have any tendency to leave the holes during use of the blade in view of the tapering nature of the pins and the presence of the shoulders and 21. The resilient piece 17 not only serves to permit the pins to enter the openings, but also assists in maintaining the parts in a firm contacting relationship without tendency toward vibration or chatter. It can be seen, therefore, that assembly of the unit is very simple, merely requiring the outer portion 6 to he slipped over the projection 5 following which the pins 14 are driven into the openings to connect the parts together.

Removal of the outer blade portion 6 is accomplished with equal facility. This is done by driving against the bottom ends of pins 14. An impact of this sort will cause the downwardly

inclined shoulders

20 and 21 to react against the lower edges of the openings 25. As a result, the

outer sections

15 and 16 of the pins will be forced toward each other against the opposition of the resilient member 17'. This allows the shoulders to enter the openings and permits the pins to be driven upwardly and removed. Therefore, the connection between the two parts of the blade assembly can be released by a few blows from a hammer. After this, the worn plate 6 can be taken 01? the base 5 and a new blade element immediately placed over the base, again to be held in place by driving the pins through the openings. No bolts are used, and the removal and attachment are accomplished merely by hammer blows. Thus, not only is installation and removal time cut to a fraction of that previously required, but also the necessity for any special equipment is obviated.

The fact that pins 14 are dimensioned so that their bottom ends project slightly beyond the lower face 8 of the blade 6 facilitates the removal operation. The exposed end is contacted by a hammer which can drive the shoulders 19 and 2h beyond the lower edge of the opening 25 before the end of the pin enters opening 26. Thus, the pin is loosened from the exterior of the unit, and it is not necessary to utilize any special implement to accomplish this.

Preferably the inner faces of the

plates

15 and 16 of the pins 14 are provided withspaced parallel transverse ribs and 31. These are located one on either plate and project inwardly approximately half of the width of the gap between the

blades

15 and 16. The

ribs

30 and 31 are spaced inwardly of the ends of the pins with the upper rib 36 being substantially opposite the shoulder 20 The ribs assist in protecting the pin units and avoid breaking the bond between the rubber lamina 17 and the

plates

15 and 16. Thus, as the plates are forced toward each other as the pins are driven into or out of the apertures, the lamina 17 will flow outwardly, including considerable movement in the longitudinal direction. This will tend to shear the bond between the rubber layer 17 and the inner faces of the plates. The ribs, however, will confine the rubber layer, limiting its relative movement with respect to the plates so that the tendency toward shearing the bond will be minimized. Furthermore, the ribs limit the amount of compression of the pins so that there can be no excessive deformation of the layer 17. Hence, even if the pin is driven through badly misaligned openings in the removable blade and support,

ribs

30 and 31 will allow only a predetermined amount of inward movement of

plates

15 and 16. Substantially metal-to-metal contact between the plates will be obtained at maximum compression, an the pin then will have characteristics approximating those of a solid element.

Alternatively for the pins 14,

ribs

30 and 31 may be omitted if the parts are arranged to accommodate the pins at a position rotated 90 from that shown in FIGURE 4.

This relationship of the parts, seen in FIGURE 6, positions the resilient lamina transversely of the removable blade instead of extending longitudinally as in the previously described embodiment. As a result, the resilient la' er again serves to lock the pin in place, but it not subject to extreme loading during installation or use of the blade. The major forces are absorbed through the side edges 32 and 33 of the plates of the pin, which do not impose a compressive force on the layer 17. Preferably edges 32 and 33 are given some taper, which may be around 7, to facilitate driving the pins into place and accomplishing a proper fit between blade 6 and its support 5.

In order to absorb any longitudinally imposed loads upon the removable blade 6, it is preferred to make the

sides

34 and 35 thicker than the webs 12. These sides also preferably are tapered in thickness so as to have a greater width at the inner edge of the recess 9 in the blade. The outer side edges of the support 5 taper in a similar manner. This facilitates assembly of the blade, achieving a snug fit and allowing lateral forces to be taken out through the

side portions

34 and 35 of the blade. Preferably the Webs 12 and their slots 13 are tapered in a similar manner.

Additionally, to preclude wear on the support 3 along the outer surface of the flange extending over the mold board 2, there may be provided a plate 36 located immediately behind the blade 6. This is a relatively thin hard steel plate that may be tack welded to the support 3. Any material passing over the support 3, therefore, contacts the plate 36 rather than the support itself. The hard plate resists abrasion in this manner and is replaceable when it becomes worn out.

, In some instances in order to conserve weight, it may be preferred to construct the wear plate unit as illustrated in FIGURE 7. Here, instead of solid webs across the recess 37, the blade member 38 is provided with spaced interconnecting posts 39 at its inner end. These interconnecting elements perform the same function as the webs in assuring that the inner end portion of the removable wear plate will not tend to open up during use. Weight and material are conserved, however, by not extending these interconnecting pieces the full width of the recess 30. The posts 39 concentrate the resisting force at the point Where the greatest stress is imposed.

From the foregoing, it can be seen that by the combination of a unique blade member adapted to fit over a projecting support and held in place by resilient drive pins, the installation and removal of blade members or similar elements requires only a minimum amount of time and practically no skill or special equipment. The removable members are extremely durable and capable of resisting any forces imposed thereon by virtue of the interconnecting spacers at the inner end of the removable piece at the location of the recesses.

The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.

I claim:

1. A removable blade arrangement comprising a support member having a projecting portion extending therefrom, a wear plate having a recess therein substantially complementarily receiving said projecting portion, said Wear plate having a duality of aligned transverse openings therein, said support member having a transverse opening in said projecting portion in alignment with said transverse openings in said wear plate, said opening in said projecting portion being larger at one end than at the other, and at said one end being of greater lateral dimension than the lateral dimension of the adjacent transverse opening in said wear plate, and a pin received in said transverse openings for holding said wear plate to said projecting portion, said pin including shoulder means at said one end of said opening in said projecting portion and converging from said shoulder means toward the opposite end of said pin, said shoulder means being inclined outwardly toward said opposite end of said pin, said pin including a resilient inner portion whereby said pin is laterally compressible.

2. A device as recited in claim 1 in which said recess in said wear plate is provided with a plurality of spaced interconnecting members extending transversely of said recess at the outer end thereof, said projecting portion having a slot corresponding to and receiving each of said interconnecting members.

3. A connector pin comprising a duality of metal plates, and a resilient lamina interconnecting said metal plates, said plates having outer sides, said outer sides including substantially fiat parallel outer faces remote from said lamina extending inwardly from one end thereof, shoulder portions at the inner edges of said outer faces remote from said end, said shoulder portions inclining outwardly toward the opposite ends of said metal plates, and outer faces remote from said lamina coverging from said shoulders to the opposite ends of said plates.

4. A connector pin comprising a duality of outer elongated members, a resilient member interposed between said elongated members, said elongated members having outwardly projecting shoulder means on the outer surfaces thereof intermediate the ends of said members, said shoulders inclining outwardly toward one end thereof, said outer members tapering from said shoulder means toward said one end thereof, and a transverse rib means on the inner face of each of said elongated members, said rib means being in spaced relationship with each other.

5. A connector pin comprising a duality of outer elongated members, a resilient member interposed between said elongated members, said elongated members having outwardly projecting shoulder means on the outer surfaces thereof intermediate the ends of said members, said shoulders inclining outwardly toward one end thereof, said outer members tapering from said shoulder means toward said one end thereof, and a transverse rib on each of said elongated members, each of said ribs extending inwardly from the, inner face of the elongated member with which it is associated toward the other of said elongated members and being received in said resilient member, said ribs beingin spaced parallelism with each other.

6. A device as recited in claim 5 in which said ribs are spaced inwardly from the outer ends of said elongated members, one of said ribs being substantially opposite the shoulder means of the elongated member with which it is associated.

7. A device as recited in claim 5 in which each of said ribs extends inwardly approximately half the thickness of said resilient member.

8. A removable blade device comprising a support member having an elongated projection therefrom; a blade member, said blade member having a recess substantially complementarily receiving said projection, said blade member having spaced interconnecting means across end portions of said recess, said projection having slots corresponding to and receiving said interconnecting means; and pin means for holding said blade member to said projection, said blade member and support member having aligned apertures at said recess receiving said pin, said apertures and said pin having cooperating shoulder means for retaining said pin in said apertures, said pin being laterally compressible and dimensioned to project beyond the adjacent outer surface of said blade at one end of said pm.

9. A device as recited in claim 8 in which said apertures include upper and lower apertures in said blade on either side of said recess, and said shoulder means in said apertures comprises the lower edge of said upper aperture in said blade, said aperture in said, su port member at a location adjacent said upper aperture being of greater lateral dimension than that of said upper aperture and tapering downwardly therefrom, said shoulder means on 6 said pin being adjacent and beneath said edge of said upper aperture, said shoulder means on said pin including sur faces on opposite sides of said pin diverging outwardly toward said one end of said pin, said pin tapering in- Wardly from said surfaces toward said one end.

10. A removable blade device comprising a support member having an elongated substantially wedge-shaped projection therefrom; a blade member, said blade member having a recess substantially complementarily receiving said projection, said blade member having spaced inter? connecting means across end portions of said recess, said projection having slots corresponding to and receiving said interconnecting means; and pin means for holding said blade member to said projection, said pin means including an elongated member having shoulder means spaced inwardly from one end thereof, said elongated member including central resilient means for permitting lateral compression of said elongated member, said projection including an aperture and said blade member including a duality of aligned apertures, said aligned apertures being in registry with said aperture in said projection, said elongated member being received within said apertures, the upper portion of said aperture'in said projection being of greater lateral dimension than the lower edge of the adjacent aperture in said blade member, said shoulder means on said elongated member being adjacent said lower edge.

11. A device as recited in claim 10 in which said shoulders taper downwardly away from said adjacent aperture in said support member for permitting removal of said pin means by imposition of force thereon at the opposite end thereof.

12. A blade assembly comprising a support member, said support member having a base flange and a laterally extending outwardly projecting portion, said outwardly projecting portion being substantially wedge-shaped in cross section and provided with a plurality of transversely extending slots therein extending from the outer edge thereof to said base portion; a wear plate received on said projecting portion, said wear plate having a substantially wedge-shaped outer contour, an inner surface adjacent said base of said support member, and a recess therein substantially complementarily receiving said projecting portion of said base member, said wear plate including spaced interconnecting means extending across said recess at said inner surface of said wear plate adjacent said base of said supporting member and received in said .slots in said support member, said wear plate and said projecting portion having aligned apertures therethrough; and pin means in said apertures for holding said wear plate on said projecting portion, said apertures in said wear plate extending through said recessed portion'thereof, said apertures in said projecting portion being larger in lateral dimension at one end than the lateral dimension of the adjacent aperture in said Wear plate, said pin means including a compressible element having shoulders extending into said larger end portion for holding said pin means in place.

13. A removable blade arrangement comprising a support member provided with an outward projection therefrom, a wear plate, said wear plate having a recess substantially complementarily receiving said projection, said wear plate and said projection having aligned apertures therein, the aperture in said wear plate including portions of smaller lateral dimension than the lateral dimension of said aperture in said projecting portion, and resilient drive pin means received in said aligned apertures, said drive pin means having a shoulder adjacent said portion of smaller lateral dimension of said aperture in said wear plate for holding said drive pin means in said apertures, said drive pin means being laterally compressible for permitting said shoulders to pass said portion of smaller lateral dimension upon installation and removal of said drive pin means, said recess including at least one interconnecting element intermediate the ends thereof, said projection having a slot therein receiving said interconnecting element.

14. A removable blade arrangement comprising a support member, said support member having a transversely elongated outwardly tapering projection extending therefrom, said projection including a plurality of spaced inwardly extending relatively narrow slots, a wear plate, said wear plate having an elongated recess in one side thereof substantially complementarily receiving said projection of said support member, said wear plate having a plurality of interconnecting webs at said side thereof extending across said recess and received in said slots, said wear plate and projection having aligned tapered apertures therein, and a drive pin complementarily received in each of said apertures for securing said wear plate to said support member.

15. A device as recited in claim 14 in which said slots are divergent from the inner ends thereof to the outer edges thereof at the distal edge of said outwardly tapering projection.

16. A device as recited in claim 15 in which said interconnecting webs are of outwardly tapering configuration and are substantially complementary to said slots in said projection of said support member.

17. A removable blade arrangement comprising a support member, said support member having an upper surface, an end surface, and a wedge-shaped projection extending outwardly from the mid-portion of said end surface, said projection including a plurality of spaced relatively narrow slots extending inwardly from the outer edge thereof toward said end surface, said slots being convergent inwardly from said outer edge; a wear plate, said wear plate including an end surface engaging said end surface of said support member, said end surface of said wear plate having an elongated recess therein substantially complementarily receiving said projection, said wear plate having spaced webs extending across said recess at said end surface and substantially complementarily received in said slots, said wear plate and said projection having aligned tapered aperture means therein; and tapered drive pin means complementarily received in said aperture means for holding said wear plate to said projection.

18. A device as recited in claim 17 in which said end surface of said wear plate projects above said upper surface of said support member, and including an additional plate on said upper surface adjacent said end of said wear plate.

19. A removable blade device comprising an elongated member, said member having two principal surfaces, said surfaces being convergent from one relatively wide side edge to the opposite relatively narrow side edge, whereby said member defines a generally wedge-shaped configuration, said member having a recess therein, said recess extending substantially the length of said member, said recess having an entrance at said relatively wide side edge and being convergent from said entrance to the inner end of said recess intermediate said side edges of said side member; and a plurality of spacedinterconca necting elements at said relatively wide edge extending transversely across said recess at said entrance thereof for strengthening said member along said relatively wide edge, said member having spaced sets of aligned apertures in said principal surfaces thereof communicating with said recess, each of said sets being adapted to receive a pin used in holding said member to a support.

20. A device as recited in claim 19 in which said interconnecting elements comprise webs extending inwardly the depth of said recess, said webs being divergent inwardly of said recess, thereby dividing said recess into a plurality of substantially trapezoidal shaped sections, each of wlu'ch is adapted to receive a tapered segment of a support member.

21. A removable blade device comprising an elongated member, said member having a first principal surface, and a second principal surface, said surfaces being convergent from a first relatively wide longitudinal side of said member to a second relatively narrow longitudinal side of said member, whereby said member is generally wedge-shaped transversely thereof, said member having a plurality of recesses extending transversely inwardly of said first side, said recesses being convergent inwardly toward said second side to an inner edge substantially parallel to said first side, said inner edge of each recess being shorter than the entrance to said recess at said first side, whereby said recesses are separated by inwardly divergent webs, said principal surfaces including a plurality of aligned pairs of apertures communicating with said recesses, whereby said recesses are adapted to receive complementary portions of a support element, and said aligned pairs of apertures are adapted to receive drive pin means for holding said member to said support element.

22. A device as recited in claim 21 in which each of said pairs of aligned apertures includes a first aperture convergent in lateral dimension from said first principal surface to said recess, and a second aperture aligned with said first aperture, said second aperture extending between said recess and said second principal surface, and being convergent in lateral dimension between said recess and said second principal surface, whereby said first and second apertures are adapted to receive a tapered drive pin extending from said first principal surface to said second principal surface and through said recess.

References Cited by the Examiner UNITED STATES PATENTS 764,577 7/04 Gilks -3 1,772,624 8/30 Brendlin 37-141 2,482,320 9/49 Clemmer 37141 2,702,490 2/55 Lauder 37-142 3,020,655 2/62 Lauder 37-142 FOREIGN PATENTS 174,734 1/35 Switzerland.

BENJAMIN HERSH, Primary Examiner. CHARLES E. OCONNELL, Examiner.

Claims

3. A CONNECTOR PIN COMPRISING A DUALITY OF METAL PLATES, AND A RESILIENT LAMINA INTERCONNECTING SAID METAL PLATES, SAID PLATES HAVING OUTER SIDES, SAID OUTER SIDES INCLUDING SUBSTANTIALLY FLAT PARALLEL OUTER FACES REMOTE FROM SAID LAMINA EXTENDING INWARDLY FROM ONE END THEREOF, SHOULDER PORTIONS AT THE INNER EDGES OF SAID OUTER FACES REMOTE FROM SAID END, SAID SHOULDER PORTIONS INCLUDING OUTWARDLY TOWARD THE OPPOSITE ENDS OF SAID METAL PLATES, AND OUTER FACES REMOTE FROM SAID LAMINA COVERING FROM SAID SHOULDERS TO THE OPPOSITE ENDS OF SAID PLATES.
14. A REMOVABLE BLADE ARRANGEMENT COMPRISING A SUPPORT MEMBER, SAID SUPPORT MEMBER HAVING A TRANSVERSELY ELONGATED OUTWARDLY TAPERING PROJECTION EXTENDING THEREFROM, SAID PROJECTION INCLUDING A PLURALITY OF SPACED INWARDLY EXTENDING RELATIVELY NARROW SLOTS, A WEAR PLATE, SAID WEAR PLATE HAVING AN ELONGATED RECESS IN ONE SIDE THEREOF SUBSTANTIALLY COMPLEMENTARILY RECEIVING SAID PROJECTION OF SAID SUPPORT MEMBER, SAID WEAR PLATE HAVING A PLURALITY OF INTERCONNECTING WEBS AT SAID SIDE THEREOF EXTENDING ACROSS SAID RECESS AND RECEIVED IN SAID SLOTS, SAID WEAR PLATE AND PROJECTION HAVING ALIGNED TAPERED APERTURES THEREIN, AND A DRIVE PIN COMPLEMENTARILY RECEIVED IN EACH OF SAID APERTURES FOR SECURING SAID WEAR PLATE TO SAID SUPPORT MEMBER
19. A REMOVABLE BLADE DEVICE COMPRISING AN ELONGATED MEMBER, SAID MEMBER HAVING TWO PRINCIPAL SURFACES, SAID SURFACES BEING CONVERGENT FROM ONE RELATIVELY WIDE SIDE EDGE TO THE OPPOSITE RELATIVELY NARROW SIDE EDGE, WHEREBY SAID MEMBER DEFINES A GENERALLY WEDGE-SHAPED CONFIGURATION, SAID MEMBER HAVING A RECESS THEREIN, SAID RECESS EXTENDING SUBSTANTIALLY THE LENGTH OF SAID MEMBER, SAID RECESS HAVING AN ENTRANCE AT SAID RELATIVELY WIDE SIDE EDGE AND BEING CONVERGENT FROM SAID ENTRANCE TO THE INNER END OF SAID RECESS INTERMEDIATE SAID SIDE EDGES OF SAID SIDE MEMBER; AND A PLURALITY OF SPACED INTERCONNECTING ELEMENTS AT SAID RELATIVELY WIDE EDGE EXTENDING TRANSVERSELY ACROSS SAID RECESS AT SAID ENTRANCE THEREOF FOR STRENGTHENING SAID MEMBER ALONG SAID RELATIVELY WIDE EDGE, SAID MEMBER HAVING SPACED SETS OF ALIGNED APERTURES IN SAID PRINCIPAL SURFACES THEREOF COMMUNICATING WITH SAID RECESS, EACH OF SAID SETS BEING ADAPTED TO RECEIVE A PIN USED IN HOLDING SAID MEMBER TO A SUPPORT.