GB2043199A

GB2043199A - Bolted joint

Info

Publication number: GB2043199A
Application number: GB8003972A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-02-08
Filing date: 1980-02-06
Publication date: 1980-10-01
Also published as: GB2043199B

Abstract

A ploughshare member (3) mountable has the outer or operative face locally dished e.g. by forging at the or each bolt hole (2) in order to form a recess or countersink (20) at the hole (2) to accommodate a bolt head (10) whereby substantially the full thickness of the member (3) is maintained at the countersink (20) to resist shear loading and ensure firm bolting especially of a case hardened member (3). The corresponding raised rear formation or boss (22) can also provide location of the member (3) in a complementary recess (42) of a support member such as a plough leg (5). The recess may be of non-circular section. <IMAGE>

Description

SPECIFICATION Formation of members for countersunk bolt mounting This invention relates to the bolt mounting of members or plates such as ploughshare members and refers in particular to the bolting of mould boards to legs or frogs of ploughs as well as the similar mounting of skims and is also applicable to the mounting of mould board fittings such as shin, point and wing pieces.

Such ploughshare members are of hardened steel to withstand wear and are secured in position by bolts having their heads countersunk so as to be flush with the operative surface of the mould board or other ploughshare member or piece.

The object of this invention is to enable an improved arrangement of such bolt mounting to be obtained whereby fracture or similar failure of the mounting is avoided or minimised.

According to this invention the operative face of a said member such as a ploughshare member is locally dished at the or each bolt hole therein in order to provide a recess or countersinking to accommodate a bolt head and whereby substantially the full thickness of the member is maintained at the recess or countersink.

The invention is further characterised by a support or other member which in use receives the ploughshare or similar member bolted thereto, being dished or recessed in a complementary manner for locating engagement with a resulting raised portion or boss at the back of the dished part of the ploughshare or similar member.

Referring to the drawings and in practice the construction and arrangement may be as follows in which: Figure 1 is a detailed sectional view showing usual countersunk bolting, and Figure 2 is a similar view showing improved countersunk bolting obtainable by means of this invention.

Referring firstly to Figure 1 the usual and well known arrangement of countersunk bolting is shown in which the head 10 of the bolt 1 is received by the countersunk part 20 of a hole 2 through a hardened ploughshare member such as a mould board 3, the shank 11 of the bolt 1 passing through a hole 4 in a leg or other support member 5 and receiving a nut 6 at the other side of the latter.

The hardened layer or skin of the mould board 3 is indicated in an exaggerated manner at 30 and tends to become of increasing thickness at sharp corners, e.g. at 30a adjacent the junction of the countersunk part 20 of the hole 2 with the remainder of the hole.

Together with the reduced thickness of the mould board 3 at this locality to a relatively thin form, the brittle case hardening at 30a tends to fracture on tightening of the bolt 1 or under the considerable shear loading to which ploughshare bolting is subjected in use. As a result the bolting becomes loose and the condition is only aggravated by tightening the bolt.

Furthermore, the thin section edge of hardened material at 30a can also have a shearing action on the bolt 1 causing the head 10 to be sheared off.

With a view to avoiding these disadvantages and to provide a much stronger bolt mounting, a typical arrangement obtainable by means of this invention is shown in Figure 2 in which the mould board 3 is dished at the bolt hole 2 to provide a recess 20 for accommodating the countersunk type head 10 of the bolt 1 and at the same time provide a full thickness of the mould board 3 behind the recess 20 containing the full depth of the hole 2.

This avoids reduction in the thickness of the mould board 3 about the hole 2 as per Figure 1 and the resulting weakness of such arrangement. Furthermore the full thickness of the mould board 3 about the bolt hole 2 in Figure 2 is less likely to fracture at the case hardening whilst the improved arrangement is such that the full thickness about the bolt shank 11 adjacent the head 10 enables the bolt mounting to withstand very considerable shear loading with little or no likelihood of the bolt head 10 being sheared off.

A further advantage of the bolting arrangement of this invention is that the raised portion or boss 22 at the back of the mould board 3 is able to locate in a complementary recess 42 in the leg 5 which recess 42 is formed by dishing the latter in a similar manner. As will be appreciated this has the effect of further strengthening the bolt mounting and resisting shear stresses whilst it also enables accurate location of the mould board 3 to be obtained in relation to the leg 5 at each bolt mounting.

The tendency of the bolt 1 to become loose is also greatly minimised owing to the absence of any thin section of mould board 3 consisting entirely or largely of brittle case hardening or carburising.

Afurther practical advantage of the improved mounting obtainable is the fact that the dishing of the mould board 3 at the bolt hole 2 to provide the recess or countersinking 20 and protrusion or boss 22 at the other side can be carried out by hot forming or forging of the mould board 3 at each hole 2 before the board is hardened. As a result machining or subsequent machining of the recess 20 and/or hole 2 is avoided or kept to a minimum.

During such forming that part of the hole 2 behind the recess 20 can be formed to any suitable noncircular form, such as a square section to receive the correspondingly formed part 12 of the bolt shank 11 so that the bolt 1 is located against rotation relative to the mould board 3. If desired the recess 20 may be of non-circular form e.g. oval to non-rotatably receive a bolt head 10 of complementary shape.

The invention also includes within its scope the arrangement of countersunk bolting which is obtainable as well as metal members such as hardened steel mould boards and other ploughshare members when formed for such bolting. The invention further includes leg or other members when dished or recessed in a complementary manner to provide location for raised back formation of the ploughshare member or similar member.

Claims

1. A member such as a ploughshare member mountable by countersunk bolt mounting is characterised by the outer or operative face of the member being locally dished at the or each bolt hole therein in order to form a recess or countersinkat the hole to accommodate a bolt head and whereby substantially the full thickness of the member is maintained at the recess or countersink.

2. A member such as a ploughshare member according to claim 1 wherein the recess or countersink at the or each bolt hole is formed in the member by a hot forming arforging operation, .3. A member such as a ploughshare member according to claim 2 wherein the recess or countersink at the or each bolt hole is formed by hotforming the member or forging the member prior to hardening of the latter.

4. A member such asa ploughshare member according to claim 1,.2 or 3 wherein at least part of the or each bolt hole or recess or countersink thereat is formed to a non-circular cross section for cooperation with a correspondingly formed part of a bolt for location of the latter against rotation relative to the member.

5. A member such as a ploughshare member according to any of claims 1 to 4 in combination with a support member which in use receives the aforesaid member bolted thereto wherein the support member is dished or recessed in a complementary mannerfor locating engagement with a resulting raised portion or boss or each thereof at the back of the dished part or parts of the aforesaid member.

6. A member such as a ploughshare member when formed for countersunk bolt mounting substantially as herein described with reference to Figure 2 of the accompanying drawing.

7. A member such as a ploughshare member and support member therefor when formed for countersunk bolt mounting and locating engagement together substantially as herein described with referpence to Figure 2 of the accompanying drawing.

9. A ploughshare mould board fitting such as a shin, point or wing piece when formed for countersunk bolt mounting according to any of the preceding claims on a mould board.

10. Countersunk bolt mounting when obtained by dished countersunk formation of a member such as a ploughshare member according to any of the preceding claims.