NZ216496A - Ladder top end safety gripper - Google Patents

Description

NEW ZEALAND PATENTS ACT. 1953 No.: 216496 Date: 11 June 1986 COMPLETE SPECIFICATION "A GRIPPING APPARATUS FOR A LADDER" I/-Wr, RAYMOND JOHN RICHARDS, a New Zealand citizen of 5 Cambridge Street, Pahiatua, New Zealand hereby declare the invention for which I /=w« pray that a patent may be granted to me1=&3-, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to a gripping apparatus for a ladder.

In forestry work a ladder is usually used to enable a person to ascend a tree for the purpose of pruning the tree or for other reasons. Typically the ladder is leaned against the tree with its bottom supported by the ground and the top supported by the tree trunk. With a conventional ladder it is usually the top rung of the ladder which rests against the tree trunk. Because of the curvature of the tree trunk there is usually only a small area of contact between it and the top of the ladder. This means that unless the bottom of the ladder is completely secure on the ground the ladder is somewhat unstable. Any movement of the bottom of the ladder can cause the top of the ladder to slip sideways against the trunk or to pivot about the trunk with the possibility of the top of the ladder separating from the trunk and the ladder falling to the ground. Even if the top of the ladder does not separate from the trunk any sudden movement of the ladder which is of sufficient magnitude may upset or dislodge any person on the ladder.

In the past various types of ladder have been devised with a view to minimising this problem with varying degrees of success. Most of these ladders are modified at their top ends to improve the grip between the top end of the ladder and the tree trunk in use. One of these ladders has a rearwardly projecting rigid arm attached at each side of the top end of the ladder and a flexible rubber belt is attached between the free ends of these arms. When the ladder is being used it is the flexible belt that is placed against the tree trunk and, because of the weight of the ladder leaning against the tree, especially when a person is on the ladder, the 3 21649 n Q C o belt assumes an arcuate shape generally conforming to the shape of the tree trunk when the two are in contact which considerably improves the stability of the top of this ladder when compared to a conventional ladder. First of all, because of the arcuate shape assumed by the flexible belt the tree trunk is located in what amounts to a recess and following on from this the area of contact between the belt and the tree trunk is much greater than the area of contact between the trunk and the top rung of a conventional ladder. However, when the ladder is used with trees having smaller and smaller diameter trunks the area of contact between the trunk and the belt decreases and the potential instability of the ladder increases. In fact for trunks of any diameter it is desirable to have as much contact as possible between the ladder top and the trunk. It was with these problems in particular in mind that the present invention was devised.

The present invention broadly consists in a gripping apparatus for a ladder comprising: a base which is attached or is attachable to or which forms part of a ladder; two arms which are spaced from each other with each being attached to the base and projecting to a common side of the base; a flexible member attached to the arms to span between the arms away from the base which flexible member can deflect inwardly towards the base when pressed against an object entering between the arms, at least one of the arms being movable towards its end to which the flexible member is attached towards the other arm whereby said deflection of the flexible member towards the base can be increased and the degree of contact between the flexible member and said object can also be increased; biasing means biasing the or each movable arm to an open position away from the other arm; and releasable securing means to secure the or each movable arm against movement away from "the other arm towards its open position unless the securing"means is released-ty^an operator. © 2 ^ 6 ^ '96 The flexible member is preferably engaged at each of its opposite ends to a O respective one of the arms away from the base.

O G Preferably one arm is pivotally attached to the base to be movable towards the other arm which is fixed to the base.

Preferably the biasing means biases the one movable arm away from the fixed arm.

Preferably the releasable securing means is used to secure the one movable arm against movement away from the fixed arm. This securing means can comprise a ratchet mechanism.

Alternatively, it is preferred that both arms are fixed to the base but one arm is resiliently flexible whereby towards its free end it is movable towards the other arm and the releasable securing means is used to secure the movable arm against movement away from the other arm.

In other embodiments of the invention both arms may be movable towards each other and biasing means and releasable securing means can be associated with both movable arms.

The present invention also broadly consists in a ladder equipped with a gripping apparatus as defined above. ^ ' "„„ 1 I ' 21.64 96 o G O o Preferably an arm is located at or towards each side of the ladder and the arms project rearwardly from the ladder.

The above gives a broad description of the present invention, some preferred forms of which will now be described with reference to the accompanying drawings in which: Figure 1 shows a front elevation of a two section ladder with the preferred apparatus of the present invention located at the top end of the upper section; Figure 2 shows to a larger scale a front elevation of the top end of the ladder and the gripping apparatus; Figure 3 shows a plan view; Figure 4 shows a side view of the gripping apparatus mounted to the top end of the ladder; and Figure 5 shows details of one preferred releasable securing means.

With particular reference to Figure 3, the preferred gripping apparatus of the present invention has a base 10, two arms 12 and 14 attached to the base and projecting to a common side of the base, and a flexible member 16, which is engaged between the arms away from the base.

.-SSR83? - ; 21 64 The base 10 can be attached or attachable to or can form a part of a ladder 18. If the gripping apparatus is attachable to a ladder it can be sold separately from the ladder and later attached to a suitable ladder. Any suitable means can be used to attach the apparatus to the ladder, for example,nuts and bolts, screws, welding, or the base can even be provided with one or more sockets into which the top end of the ladder is received. Where the base forms part of the ladder it can form a rung or step of the ladder, usually located at the very top end of the ladder. Alternatively, the sides or legs of the ladder can provide the base. If the apparatus is detachable from the ladder the ladder can then be used in a conventional way.

As has been stated the arms 12 and 14 project to a common side of the base, that is, they project rearwardly from the ladder in use. In the drawings the arms are shown projecting approximately at right angles from the base though they can project at other angles. The arms are preferably made from metal channel, for example, aluminium, or an alloy thereof for a combination of strength and lightness.

In the preferred form of the invention the arm 12 is fixed to the base whereas the arm 14 is pivotally mounted at 20 to flanges 22 attached to the base 10 so that the arm 14 is pivotally movable towards the fixed arm 12.

The preferred flexible member 16 is a band or belt made of any suitable material such as canvas^^or leather, or rubber, for example. At each end this belt is engaged at 24 to a^res^ective one of the arms 12 and v'v* ,1» L. Xfrvsey ' .

■"KUVtVfH ■ o P ' " , 14. The points where the belt engages with the arms 12 and 14 are located away from the base 10 so that the belt can deflect inwardly towards the base, such as shown in Figure 3, when the belt is pressed by an object entering the space 26 between the arms. In forestry work the object will usually be the trunk of a tree, although in other uses it could be a pole such as a power pole, for example, or a post or the like.

The present invention offers a particular advantage .by having at least one of the arms movable towards the other in that the deflection of the belt 16 towards the base can be increased which means" that for any diameter trunk and for smaller diameter trunks in particular the shape of the belt will conform better to the shape of the trunk where the two are in contact, this increasing the area of contact between the belt and the trunk and thereby increasing the stability of the ladder. Furthermore, the trunks are in effect contained within a deeper recess so that the arms 12 and 14 themselves are more effective in functioning as lateral stops limiting the possible sideways movement of the ladder against the trunk.

Because it is easier to place the apparatus against a trunk when the movable arm is in an open position the preferred apparatus includes biasing means whereby the movable arm 14 is biased away from the fixed arm 12 towards an open position as shown in Figure 3. The biasing means is not shown but can comprise a coil spring located about the pivot pin 20 with spring arms of the coil spring in contact with the base 10 and with the movable arm 14 to urge that movable arm to its open position. c - .ay fiagv *#&** *> --,.

I l :: - a - ~ ^ P i i\ ~ > The preferred gripping apparatus also includes releasable securing means -4 which functions to secure the movable arm 14 against movement away from I the fixed arm 12- This means that once the movable arm is moved to a v O position towards the fixed arm the movable arm cannot be returned to its open position until the securing means is released. This prevents any swinging back and forth of the movable arm 14 and the belt 16 with any ? | bouncing movement of the person on the ladder and hence also contributes to the stability of the ladder in use. The preferred securing means comprises a ratchet mechanism. In Figure 3 one end ofa ratchet arm 28 is pivotally attached at 30 to the movable arm 14 and the other end 32 passes through a hole in the fixed arm 12. This end of the ratchet arm has ratchet teeth engagable with a side of the hole in the fixed am to prevent opening movement of the movable arm when the ratchet is engaged. The ratchet arm can be moved to disengage the ratchet teeth from the side of the hole in the fixed arm and allow opening movement of the movable arm 14. If desired the ratchet arm can be biased, for example, by a spring or by gravity, so that the ratchet teeth normally engage the fixed arm so that a deliberate action by the person using the ladder is necessary to disengage the ratchet arm. In this case the ratchet arm may be disengagable by remote means, for example, a linkage or cord may be connected to the ratchet arm so that it can be disengaged by a person standing on the ground.

Figure 5 shows in perspective view details of an alternative releasable securing means. A rod 28' is pivotally attached at 30' to the movable arm 14. Like the ratchet arm 28 of Figures 2 and 3, the rod 28' has a bend in it so that towards its free end it lies generally parallel to the base 10. i This end of the rod passes through holes in a pivotal bracket 40 and a * fixed bracket 42. The fixed bracket is fixed to the base 10 and the v; * pivotal bracket is pivotal relative to the base 10 between a position ^fffl where the holes in the brackets are slightly out of alignment, with the hole in the pivotal bracket not being square to the rod, and a position where the holes are substantially aligned, with the hole in the pivotal •*: I bracket being substantially square to the rod. A spring 44 biases the I © i pivotal bracket so that the holes are out of alignment whereby the pivotal t | bracket locks with the rod to prevent the movable arm 14 from moving i towards its open position. To release the movable arm 14 and allow it to return to its open position a rope 46 attached to the free endof the pivotal bracket 40 can be pulled to force that bracket to move so that the holes are aligned and the rod 28' can slide through them. The rope can be long enough to be pulled from the ground.

In Figure 1 the gripping apparatus is shown attached at the top end of the upper section of a ladder comprising two sections 18a and 18b. The top section 18a can be used by itself or, when extra height is required, used in conjunction with the lower section 18b. The ladder shown is of the type having two side legs 34 and 36 joined by a plurality of rungs or steps 38. However, the gripping apparatus can be used with other types of 4"*"S ladder, for example, a ladder having a single longitudinal member to which the steps or rungs are attached at their centers. With this type of ladder it is desirable that there be flanges or other forms of stop at the ends of the steps or rungs to prevent a person's foot from slipping off the step or rung. 21649- The above describes the preferred form of the invention and indicates some possible modifications but various other modifications can be made without departing from the scope of the invention as has been broadly defined.

In another embodiment of the invention both arms 12 and 14 are fixed to the base 10 but one of the arms is made to be resiliently flexible whereby towards its free end it is movable towards the other arm when an inwards force is exerted on that arm from the belt 16. Again a releasable securing means is preferably provided to secure the movable arm against movement away from the other arm until the securing means is disengaged. In other embodiments of the invention both arms may be made to be movable towards each other. In such cases both arms can be pivotally mounted to the base 10 or can be made to be resiliently flexible or one arm can be pivotally mounted to the base and the other arm made to be resiliently flexible. Again, it is preferred that biasing means and releasable securing means be associated with one or preferably both of the movable arms. Where any arm is made to be resiliently flexible a biasing means is inherent in the construction of the arm. The gripping apparatus and the ladder will normally be made of lightweight components, preferably made from aluminium alloy.

At their bottom ends the side legs of the upper section of the ladder are preferably flared outwardly whereas for the lower section the top ends of the legs are angled inwardly so that the ladder sections can mate together as shown in Figure 1. The ladder sections can then be bolted together. At their bottom ends the legs of both the upper and lower sections of the 216496 - ii - ladder are preferably cut to be angled rearwardly, for example, by about 45 degrees so that these ends when placed on the ground tend to dig in for extra stability.

In another modification of the invention the gripping apparatus can be pivotal with respect to the ladder, the pivotal axis being parallel to the base 10. This allows adjustment when the ladder is inclined at different angles to the trunk or pole or the like. Locking means can be provided to lock the apparatus at a particular angular setting. The ends of the belt 16 could also be attached to the arms by a single bolt or like attachment to allow for swivelling of the belt relative to the arms.

While the preferred flexible member comprises a single belt it could comprise a chain or a plurality of straps or cords instead. The engagement of one or both ends of the belt with the arm or arms can be made to be adjustable so that the length of belt between the arms can be altered. This means that for any spacing of the arms, the possible deflection of the belt, i.e., its possible curvature, can be altered by altering the setting of the belt with respect to one or both arms. Known types of buckles or belt clamps can be used for this purpose.

Claims (18)

216496 12 WHAT I CLAIM I?
1. A gripping apparatus for a ladder, comprising: a base which is attached or is attachable to or which forms part of a ladder; two arms which are spaced from each other with each being attached to the base and projecting to a common side of the base; a flexible member attached to the arms to span between the arms away from the base which flexible member can deflect inwardly towards the base when pressed against an object entering between the arms, at least one of the arms being movable towards its end to which the flexible member is attached towards the other arm whereby said deflection of the flexible member towards the base can be increased and the degree of contact between the flexible member and said object can also be increased; biasing means biasing the or each movable arm to an open position away from the other arm; and releasable securing means to secure the or each movable arm against movement away from the other arm towards its open position unless the securing means is released by an operator.
2. 2. An apparatus as claimed in claim 1 wherein the flexible member is engaged at each of its opposite ends to a respective one of the arms away from the base.
3. 3. An apparatus as claimed in claim 1 or claim 2 wherein the flexible member comprises a flexible belt. 216496 - 13 -
4. An apparatus as claimed in any one of the preceding claims wherein one or each of the arms is pivotally attached to the base to be movable towards the other arm.
5. An apparatus as claimed in any one of the preceding claims 1 to 3 wherein one arm is pivotally attached to the base to be movable towards the other arm which is fixed to the base.
6. An apparatus as claimed in any one of the preceding claims 1 to 3 wherein both arms are fixed to the base but one or each of the arms is resiliently flexible whereby towards its free end it is movable towards the other arm.
7. An apparatus as claimed in any one of the preceding claims 1 to 3 wherein both arms are fixed to the base but one arm is resiliently flexible whereby towards its free end it is movable towards the other arm which is a substantially rigid arm.
8. An apparatus as claimed in any one of the preceding claims wherein the releasable securing means comprises a ratchet mechanism.
9. An apparatus as claimed in claim 8 wherein the ratchet mechanism comprises a separate ratchet arm pivotally attached to the or each movable arm, the or each ratchet arm having a free end with ratchet teeth engagable in any one of a plurality of positions with the side of a hole in a fixed part of the apparatus, in"^hici^hole said free nV'-. '' - \ ' • ;,.., •• 1 . - , ; ■ ' - - 216496 14 - r>
10. 10. An apparatus as claimed in claim 9 wherein the ratchet arm is biased against the side of the hole to engage therewith but can be disengaged by an operator to release the securing means.
11. 11• An apparatus as claimed in any one of claims 1 to 7 wherein the releasable securing means comprises a separate elongated member pivotally attached to the or each movable arm, the or each member passing through holes in a pivotal bracket mounted to the base and in a fixed part of the apparatus, whereby the pivotal bracket is pivotal between a position where its hole is substantially aligned with the other hole to permit sliding movement of the member in said holes and a position where said holes are out of alignment so that the pivotal bracket locks on the member to prevent movement of the movable arm to its open position. e
12. 12. An apparatus as claimed in claim 11 wherein the pivotal bracket is biased to its locking position but can be released therefrom by an operator. o
13. 13. A gripping apparatus for a ladder, substantially as herein described with reference to any embodiment shown in the accompanying drawings.
14. 14. A ladder equipped with a gripping apparatus as claimed in any one of the preceding claims.
15. 15. A ladder as claimed in claim 14 wherein the gripping apparatus is located at the top end of the ladder. 216-196 - 15 -
16. 16. A ladder as claimed in claim 14 or claim 15 wherein an arm of the gripping apparatus is located at or towards each side of the ladder and the arms project rearwardly from the ladder.
17. 17. A ladder as claimed in any one of the preceding claims 14 to 16 wherein the gripping apparatus is pivotally mounted to the ladder, the pivot axis being parallel to the base.
18. 18. A ladder as claimed in any one of the preceding claims 14 to 17 and substantially as herein described with reference to any embodiment disclosed. OATEO THIS ^ DAY OF fOootwUeoi 19^0 A. J. PARK ft SON AGENTS FOR THE APPLICANTS //* V- #jPv^