GB2070125A - Improvements in twistlocks for mounting freight containers on trailers and other vehicles - Google Patents

Abstract

The invention relates to twistlocks of the retractable type. The twistlock body has a flat upper surface with an oval opening 3 through which the T-head 9 and shear member 17 are raised to erect the twistlock for use. The raised head 9 and member 17 are rotated through 90 DEG and lowered to a recess in an upper surface 2 of the body which supports and locates the shear member 17. A container is lowered on to the twistlock so that its corner fitment is entered by the T-head 9 and the shear member 17. Yield of a spring loaded detent ball 31 permits rotation of the T-head 9 through 90 DEG to lock the corner fitment. A slot 32 and opening 19 in the shear member 17 permit the T-head 9 to be drawn down upon rotation of a nut 14 on a screw- threaded shank 11 to abut the bottom 24 of the body, so preventing accidental release of the twistlock. <IMAGE>

Description

SPECIFICATION Improvements in twistlocks for mounting freight containers on trailers and other vehicles This invention relates to twistlocks of the retractable type for locating and retaining freight containers on trailers and other vehicles during transport.

Freight containers are built with a standard corner fitment, usually a casting, at each corner.

The fitment has a generally oval opening in its lower face leading to a cavity which includes a flanged recess extending over the minor axis of the opening. A T-threaded pin and a shear member, mounted on or carried by the pin, each have a plan shape which corresponds to that of the opening so that they may be entered into it.

The pin is then rotated through substantially 900 so that the major axis of the T-head is substantially parallel to the minor axis of the opening and normal to the major axes of the shear member and the opening. The T-head is engaged in the recess. This is the "lock" position.

Conversely, in the "unlock" position the major axes of the T-head, shear member and opening are substantially parallel to one another. The shear member and pin are movable up and down in a body of the twistlock between an erected position for engagement in a corner fitment and a lowered or retracted position in which neither protrudes above the upper surface of the body. Such a twistlock is hereinafter referred to as "of the type described".

Increasingly stringent safety and operational requirements call for enhanced strength and reliability of twistlocks and these have to be provided within the dimensional limitations imposed by the standardised corner fitment, thereby imposing considerable design problems. A proposed new standard doubles the tensile load which the pin is required to withstand, from 5 tonnes to 10 tonnes.

The present invention consists in a twistlock of the type described comprising a body with a substantially flat upper surface having a generally oval opening therethrough, a recess in the upper surface adapted to locate and support the shear member after it has been raised through the opening, rotated through substantially 900 and lowered thereinto, the body including a rear wall and two side walls defining an enclosure within which the shear member is movable up and down but within which the shear member is not rotatable, the shear member having opposed upstanding limbs defining a channel-shaped opening between them, the T-headed pin having a shank which passes through the shear member, means acting between the shank and the shear member to cause the shear member to be raised when the shank is caused to move upwardly in the body, means to rotate the pin, co-operating means on the shank and shear member whereby the shear member can be rotated by the shank, the co-operating means being releasable where by the shank can be rotated independently of the shear member when the latter is located by the recess or within the body, and means to permit axial movement of the pin relative to the shear member when the major axes of the T-head and shear member when the major axes of the T-head and shear member are n ormal to one another whereby the T-head can enter into the channelshaped opening.

The shank may have a screw-threaded portion below the shear member and a co-operating threaded nut may be adapted, on tightening against the bottom of the body, to draw the Thead down on to and retain it against the flanges of the recess in the corner fitment of a freight container when the pin is in the "lock" position.

Such a screw thread is preferably rolled or forged on the shank of the pin. Drain holes may be provided in the bottom of the body.

The body may have two external ribs, each rib having a generally vertical edge and a generally horizontal edge. The former edge may be integral with or secured to either a rear wall of the body or an enclosure defined by rear, front and side walls of the body. The latter edge may be integral with or secured to the underside of the upper surface of the body and may extend from the rear wall or enclosure as the case may be to, or adjacent to, a front corner of the upper surface of the body. Such ribs will serve to strengthen the upper surface of the body.

The body is preferably a casting.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a front elevation showing a twistlock in a raised and unlocked position for entry into a corner fitment of a freight container, Figure 2 is a plan view of the twistlock in the position of Figure 1, Figure 3 is a side elevation of the twistlock in a "lock" position, Figure 4 is a partly sectioned side elevation of the twistlock in a retracted position, Figure 5 is a fragmentary section on line 5-5 of Figure 2, Figure 6 is a fragmentary view in elevation of means for rotating the pin, Figure 7 is a view, corresponding to Figure 1, of a modified twistlock, Figure 8 is a side elevation of the modified twistlock in the position shown in Figure 7, and Figure 9 is a view, corresponding to Figure 4, of the modified twistlock.

Referring to Figures 1 to 6, the twistlock has a body 1 which comprises a steel casting having a substantially flat upper surface 2 with a substantially oval opening 3 through it. The body has a front wall 4, a rear wall 5 and side walls 6 which define an enclosure 7.

Verticaliy and rotatably movable in the body 1 is a locking pin 8 which has a T-head 9 at the top end and a shank 11 which terminates at its lower end in a reduced diameter portion 12. Above portion 12 the shank is screw threaded, as at 13.

A correspondingly threaded nut 14 is engaged on the screw thread 13. Portion 12 is drilled diametrically to receive a bar 1 5 which is secured by a pin 1 6. The bar 1 5 constitutes means for rotating the locking pin 8.

Also vertically movable, but not rotatable, in the body is a shear member 1 7 of the same shape in plan as the T-head 9. This shape also corresponds to that of the opening 3, the enclosure 7 and the opening in the lower face of a corner fitment of a freight container but is dimensionally slightly smaller so that the shear member 1 7 and the Thead 9 can slide up and down in the enclosure and enter the corner fitment. The walls of the enclosure constitute guide surfaces for the shear member 17 and T-head 9.

Along its vertical axis the shear member 17 is generally U-shaped, having opposed upstanding limbs 1 8 at each end which define a channel shaped opening 1 9 between them. The shear member 17 has a central circular opening 21 through which the shank 11 of the locking pin 8 passes. A circlip 22 located in a groove in the shank 11 retains the shear member 17 on the shank, adjacent the T-head 9. The shank 11 also passes through a circular opening 23 in bottom wall 24 of the body. Drain holes for the body are provided at 25.

A bore 26 in the shear member 17 slidably receives a detent ball 27, a spring 28 and a screwthreaded plug 29. The shank 11 is indented at 31 to provide a seating location for the ball 27 when the major axes of the T-head 9 and shear member 17 are parallel to one another. The shank 11 has an axially extending indentation or slot 32 which extends towards the T-head 9 and, at its lower end, is in transverse alignment with the indentation 31.

The indentations 31,32 are duplicated at diametrically opposed positions 31 a, 32a respectively. Slots 32, 32a are circumferentially spaced 900 from indentation 31,31 a.

The upper surface 2 of the body is recessed at 33 so as to provide, above the reinforced by the side walls 6, a platform 34 which supports and locates the shear member 1 7 when in the raised position, as seen best in Figure 5.

The operation of the twistlock will now be described. In the position shown in Figure 4, the twistlock is retracted, that is to say the shear member 1 7 and T-head 9 lie within the enclosure 7 so that neither protrudes above the upper surface 2. The nut 14 is at the lower end of the screw thread 13.

The twistlock is erected for use by applying an upward force to the locking pin 8, for example by means of the bar 1 5, so as to raise the shear member 17 clear of the upper surface 2. The bar 1 5 is then used to rotate the pin through 900 so that the major axis of the T-head 9 now lies transversely of the body and is aligned with the recess 33 and the platform 34 (Figure 2). Because of the action of the spring 28, ball 27 and indentation 31, the shear member 1 7 also similarly rotates through 900. Next the locking pin is lowered so that the shear member 1 7 sits in the recess 33 upon platform 34 (Figures 1, 2, 5). A freight container is then lowered so that the Thead 9 and shear member 17 enter the opening in the lower surface of a corner fitment.The bar 1 5 is again turned through 900 (in either direction from the Figure 2 position) turning the T-head 9 so that its major axis is normal to that of the shear member 1 7 and the T-head is engaged in the flanged recess in the corner fitment. This movement is permitted by yielding of the spring 28. The ball 27 is thus engaged in the slot 32 or 32A and the T-head 9 enters the channel shaped opening 1 9 in the shear member 1 7 preventing rotation back to the unlocked position. The nut 14 is finally screwed up to engage the bottom wall 24 of the body, so preventing lifting of the pin and any possibility of accidental unlocking of the twistlock.

These operations are reversed to unlock and retract the twistlock.

It will be seen by reference to Figure 1 that when the twistlock is in the erected position the length of the screw thread 1 3 on the shank 11 is sufficient to allow the nut 14 to be screwed up against the bottom wall 24 of the body to secure the twistlock in the erected position and prevent accidental retraction. Thus, the provision of the threaded shank and nut serve both as a safety feature and to prevent undesirable wear and noise which might otherwise be caused by the parts rattling due to motion of the vehicle to which the twistlock is fitted.

The screw thread on the pin may be cut.

However, in order to enhance the strength of the pin it is preferred that the screw thread is formed on the shank 11 by a forging or thread rolling operation. The preferred thread form is ACME.

This may be a full depth ACME, two thirds or stub ACME. The crests and roots will be radiussed in conformity with thread rolling practice.

The nut 14 may be made as casting. The shear member 1 7 is desirably either a casting or a forging to eliminate machining.

The further embodiment illustrated by Figures 7, 8 and 9 will now be described. Parts corresponding to those described in the previous embodiment are indicated by corresponding references. The body 1 is a casting and has external ribs 40, 41 cast integrally with it. Each rib has a generally vertical edge and a generally horizontal edge. The former edge may be integral with or secured to either a rear wall of the body or an enclosure defined by rear, front and side walls of the body. The latter edge may be integral with or secured to the underside of the upper surface of the body and may extend from the rear wall or enclosure as the case may be to, or adjacent to, a front corner of the upper surface of the body. Such ribs will serve to strengthen the upper surface of the body.

In this modified twistlock the bottom wall 24 (as seen in Figure 9) is deeper than that shown in Figure 4. The increased depth improves guidance of the locking pin 8 during raising and lowering.

The screw thread at 13 on pin 8 is continued further along the shank, thus enabling the nut 14 to be screwed up to the bottom wall 24 to secure the pin 8 in the retracted position. The nut 14 has three lobes instead of four and the depth of the rear wall 5 is increased.

A suitable material for manufacture of the Tthreaded pin is Specification 080M40 to be found in B.S.970 Part 1. A suitable (casting) material for the body shear member and nut is B.S.3100 1976 AL1. A similar grade of material will be suitable for the shear member and nut when these are forged.

The constructions described herein provide rugged twistlocks of adequate strength to meet new requirements, combining important safety features with relatively low manufacturing costs resulting from the minimising of machining operations and use of a minimum number of component parts.

Claims (13)

1. A twistlock of the type described comprising a body with a substantially flat upper surface having a generally oval opening therethrough, a recess in the upper surface adapted to locate and support the shear member after it has been raised through the opening, rotated through substantially 900 and lowered thereinto, the body including a rear wall and two side walls defining an enclosure within which the shear member is movable up and down but within which the shear member is not rotatable, the shear member having opposed upstanding limbs defining a channel-shaped opening between them, the T-headed pin having a shank which passes through the shear member, means acting between the shank and the shear member to cause the shear member to be raised when the shank is caused to move upwardly in the body, means to rotate the pin, co-operating means on the shank and shear member whereby the shear member can be rotated by the shank, the co-operating means being releasable whereby the shank can be rotated independently of the shear member when the latter is located by the recess or within the body, and means to permit axial movement of the pin relative to the shear member when the major axes of the T-head and shear member are normal to one another whereby the Thead can enter into the channel-shaped opening.

2. A twistlock as claimed in Claim 1 including stop means on or in the body defining a retracted position of the shear member and T-head.

3. A twistlock as claimed in Claim 1 or 2 including means on or in the body +o guide the shank for up and down movement and rotation relative to the body.

4. A twistlock as claimed in Claim 3 in which the guide means comprises a bottom wall of the body with an opening therethrough in which the shank is guidably received.

5. A twistlock as claimed in Claim 4 as dependent from Claim 2 in which the bottom wall provides a stop against which the shear member abuts when in a retracted position.

6. A twistlock as claimed in any preceding claim in which the body has two external ribs, one on each side of the body, each rib having a generally vertical edge and a generally horizontal edge such that the vertical edges are integral with or secured to the rear wall of the body and the horizontal edges are integral with or secured to the underside of the upper surface of the body and extend form the rear wall to, or adjacent to, respective front corners of the upper surface of the body.

7. A twistlock as claimed in any of Claims 1 to 5 in which the body has two external ribs, one on each side of the body, each rib having a generally vertical edge and a generally horizontal edge such that the vertical edges are integral with or secured to respective side walls of the enclosure and the horizontal edges are integral with or secured to the underside of the upper surface of the body and extend from the respective side wall to, or adjacent to, a respective front corner of the upper surface of the body.

8. A twistlock as claimed in any preceding claim in which the shank has a screw-threaded portion spaced along the shank from the T-head and a mating nut on the screw-threaded shank portion, the arrangement being such that with the twistlock engaged with and locked to a corner fitment of a container the nut may be screwed along the shank towards the T-head to abut against a portion of the body and so secure the twistlock against accidental unlocking.

9. A twistlock as claimed in any of Claims 1 to 7 in which the shank has a screw-threaded portion spaced along the shank from the T-head and a mating nut on the screw-threaded shank portion, the arrangement being such that with the T-head and shear member retracted the nut may be screwed along the shank towards the T-head to abut against a portion of the body and so secure the T-head and shear member in the retracted' position.

10. A twistlock as claimed in Claim 8 or Claim 9 in which the screw thread on the shank is formed by a thread rolling process.

11. A twistlock as claimed in Claim 8 or Claim 9 in which the screw thread on the shank is formed by a forging process.

1 2. A twistlock substantially as described herein with reference to and as illustrated by Figures 1 to 6 of the accompanying drawings.

13. A twistlock substantially as described herein with reference to and as illustrated by Figures 2 and 5 to 9 of the accompanying drawings.