GB2056244A - Animal trap - Google Patents

Abstract

An improved trap for catching small animals, such as rodents, and the like, comprises a door mechanism 25, 26 having a door 26 to close an entry port through which the animal enters the trap, in which the mechanism is arranged to pivot about an axis 27 which is spaced from the door whereby the door closes the entry port by pivotal motion across the entry port. This arrangement of door mechanism advantageously diminishes the risk of the door striking and injuring the animal. <IMAGE>

Description

SPECIFICATION A trap for catching small animals This invention relates to a trap for catching small animals, particularly for use for educational and research purposes.

During field studies of small animals such as rodents and the like, it is customary to trap the animals to obtain information concerning population, feeding habits, disease and other matters. The traps used are normally of the type which permit live retrieval of the animals so that they may be studied and subsequently returned to the wild.

Currently available small mammal traps are generally constructed from aluminium sheet, usually in the form of a rectangular cross-section tube, or pair of interlocking tubes, having an entrance at one end with a door hinged at the entrance about a horizontal axis and arranged to be tripped by the animal after it has entered the trap so as to drop down or spring up from within the trap thereby trapping the animal inside. These traps, however, are not wholly satisfactory as the animals may be injured by the door mechanism when the door closes.

An improved trap for catching small animals has now been devised which diminishes the risk of the animal becoming harmed by the closing door mechanism.

According to the present invention an improved trap for catching small animals comprises a door mechanism having a door to close an entry port through which the animal enters the trap, in which the mechanism is arranged to pivot about an axis which is spaced from the door whereby the door closes the entry port by pivotal motion across the entry port.

In view of the positioning of the door mechanism pivot and the pivotal motion which the door executes across the entry port, the door of the present invention sweeps out a relatively smaller volume when the door closes than doors of prior art traps in which the door itself is hinged at the entry port. In consequence the risk of the door striking and injuring the animal is decreased as compared with prior art traps. For example, in use the trap is set with the door adjacent the entry port and on triggering of the trap the mechanism pivots about the axis, usually under a biassing influence such as a spring, and the door moves across and closes the entry port.In particularly preferred embodiments the trap wall is arcuate with respect to the axis of rotation of the door mechanism adjacent the entry port and the door is similarly profiled such that as the door closes it slides across the entry port in close proximity with the wall of the trap and the internal volume sweep out by the door is substantially minimised.

In one embodiment the door mechanism comprises a radial arm pivotted towards one end and carrying or encompassing the door towards its other end. The door may lie in the plane of the radial arm, or more preferably is disposed transverse to the radial arm. Preferably also, the axis of the door mechanism passes through the trap; for instance, the axis passes vertically through the floor of the trap spaced towards the end of the trap opposite the entry port.

The trap typically has a trigger mechanism adapted to be triggered by the animal so as to cause the door to close, and this trigger mechanism is usually located within the trap spaced from or arranged in relation to the entry port so that the door is not triggered until the animal has entered fully into the trap. In one form this trigger mechanism comprises a false floor or treadle across the bottom of the inside of the trap which maintains the door in the open position e.g.

against a biassing influence, and is responsive to the weight of the animal e.g. is pivotted to trigger the trap and release the door. The radial arm of the door mechanism may be located beneath such a false floor trigger mechanism which may thereby conveniently shield the trapped animal from the rotating arm when the trap is triggered.

It will be appreciated that the trap will normally comprise a locking mechanism for locking the door in the closed position, to prevent the trapped animal from escaping and also to guard against predators breaking into the trap and harming the trapped animal. In addition, however, the trap may have a pre-baiting mechanism for locking the door in the open position e.g. so that animals may familiarise themselves with the interior of the trap prior to trapping. Preferably the locking and prebaiting mechanisms are provided by a single mechanism. For instance, a latch mechanism is provided which is adapted to either latch in front of the leading edge of the door in the pre-baiting mode or latch behind the trailing edge of the door in the locking mode.

Preferably the trap of the invention has a means of access which is separate from the door entry port, and which may advantageously provide for greater ease of retrieval of the catch. For instance, the trap has a detachable lid or cover e.g. a sliding lid, to provide this separate means of access.

It will be appreciated that the trap and entry port may be any suitable size and these may be varied in accordance with the species and/or size of animal for which the trap is intended. Preferably the entry port is substantially circular in shape.

The trap of the invention may be made of any suitable material including metal, though preferably the trap is constructed of a plastics material and in preferred embodiments traps according to the invention are particularly amenable to manufacture by customary plastics forming techniques such as vacuum forming.

Advantageously also the use of a plastics material substantially decreases the insulation and condensation problems which are encountered with prior art traps made from metal sheet.

Moreover, use of plastics materials may conveniently provide a light-weight trap which is easier to transport in quantity than prior art metal traps.

Preferably the interior of the trap is constructed with the minimum of free edges which may be gnawed by the trapped animal. In this regard, the whole or part of the door mechanism, in particular the barrier, may have a hard metal edging, or even be constructed totally of hard metal, to resist the effects of gnawing.

The invention is further described by way of illustration only in the following description which refers to the accompanying diagrams, in which: Figure 1 shows a part cut away perspective view of a trap according to the invention having a sliding lid which is shown drawn almost completely off the trap enclosure; Figure 2 shows an end elevation of the entry port end of the enclosure of the trap of Figure 1; Figure 3 shows a side elevation in part section of the enclosure of the trap of Figure 1; Figure 4 shows a plan view of the enclosure of the trap of Figure 1; Figure 5 shows a plan view of the radial door of the trap of Figure 1;; Figure 6 shows a sectional elevation view of the radial door of Figure 5 taken along the line VI--VI of Figure 5 viewed from the direction of the arrows, Figure 7 shows a plan view of the false floor treadle trigger mechanism of the trap of Figure 1, and Figure 8 shows a side elevation view of the trigger mechanism of Figure 7 viewed from the direction of the arrow.

The small animal trap illustrated in the accompanying diagrams comprises four main components, a trap enclosure 1, a sliding lid 2 therefor, a door mechanism 3 and a false floor treadle trigger mechanism 4 for the door, all of which are made from suitably moulded and shaped polypropylene plastic sheet.

The enclosure 1 is an open-topped box produced in a single piece from a sheet of polypropylene plastic by vacuum forming. The enclosure has a flat base 5 having a pair of convexly arcuate end edges and a pair of parallel straight side edges. The walls 6a, 6b, 7 and 8 of the enclosure rise from the base splaying outwardly from the vertical such that the enclosure 1 is of general overall bath-tub shape.

The flat rhomboid shaped side walls 6a and 6b extend upwardly at angles of about 1 50 to the vertical from the straight edges of the base..From the arcuate end edges of the base correspondingly arcuate end walls 7 and 8 extend, the front end 7 and rear end 8 being splayed outwardly to the vertical at angles of about 200 and about 400 respectively. The radii of curvature of the ends 7 and 8 are substantially the same and slightly less than the maximum length of the base. Around the tops of the enclosure walls runs an outwardly turned flange 10 of substantially constant width lying in a plane parallel to that of the base. This flange 10 constitutes the remainder of the periphery of the original plastic sheet left after vacuum forming of the enclosure, and the portions of this flange which run along the tops of the side walls 6a and 6b conveniently provide runners for the sliding lid 2.This lid 2 is a flat plastic sheet having substantially the same shape as the area bounded by the periphery of the flange 10.

Extensions to the straight edges of the lid are turned under along their lengths to form elongate channels (not shown) which receive the straightedged portions of the flange 10 so as to guide the sliding lid 2 on and off the top of the enclosure.

A circular entry port 1 2 is cut into the front end 7 of the enclosure offset towards the side 6b thereof. The entry port 12 provides a means of access for the small animal to enter the enclosure 1 and as shown in the accompanying diagrams has a diameter of about 20mm which is suitable for catching small mammals such as shrews and voles; though larger size entry ports e.g.

25-35mm, are required for catching larger animals. Two smaller holes 13 and 14 are also provided on a level through the front end 7 of the enclosure towards the bottom thereof, one hole 13 being at the centre of the end 7 and the other 14 offset towards the side 6a of the enclosure.

With reference to Figures 1 and 4, these holes 1 3 and 14 accommodate a metal spring clip 5 which has a pawl 1 6 passing through the hole 1 3 into the enclosure to provide a latch for locking the door 3 in the open position for pre-baiting or in the closed position to retain the catch in the trap. At the middle of both the sides 6a and 6b and towards the bottoms thereof intermediate-sized holes 1 7a and 1 7b are provided to act as pivot points for the false floor treadle trigger mechanism 4.Also a smaller hole 1 8 is drilled through the side 6a towards the base 5 and the back 8 of the enclosure for holding one end of a metal wire spring 1 9 which provides the biasing means for closing the door 3. Four holes 20, of diameter about 3mm, are drilled through the base 5, equispaced one at each corner thereof, to provide for drainage from the trap enclosure. In addition, at the middle of the base 5 and adjacent the back edge thereof is a raised portion 22 having a vertical hole 23 drilled through the centre of it for accommodating the pivot pin (not shown) of the door mechanism. The corresponding recess 24 provided in the underneath surface of the base conveniently accommodates the head of the door mechanism pivot pin.

With reference to Figures 5 and 6, the door mechanism 3 comprises a single piece of polypropylene plastic sheet having a radial arm portion 25 and a door 26 for closing across the entry port 12. The radial arm portion 25 is in the form of a planar equilateral triangle having a hole 27 drilled through at the apex end. At the base end of the equilaterally triangular arm 25 is a convexly arcuate edge from which the door 26 extends upwardly inclined away from the plane of the arm at an angle of about 1100. The door is curved about an axis perpendicular to the plane of the arm 25 through the hole 27, has parallel longitudinal edges and terminates at its end in an edge parallel to the plane of the arm 25. Towards the base end, both radial edges of the arm 25 have moulded indentations 28.

With reference to Figure 1 , the door mechanism 3 is attached to the base 5 of the enclosure by a pivot pin 30 which also passes through the hole 23. Thus the door mechanism is able to pivot within the enclosure, with the door 26 sliding across, and in close proximity with, the internal surface of the front end 7 of the enclosure to which its surface curvature closely conforms. In consequence, the volume of the interior of the trap which is swept out when the door closes is substantially minimised. The combination of the indentations 28 on the edges of the arm 25 and the raised portion 22 on the enclosure base 5 serve to keep the door mechanism out of contact with the base 5 and thereby diminish the risk of the door mechanism 3 becoming fouled e.g. by nesting material.The door mechanism 3 is biassed by the wire spring 1 9 so that the barrier 26 slides across and closes the entry port 12, a hook on the free end of the spring 1 9 being hooked over the trailing edge of the door arm 25. When the barrier 26 has closed across the entry port 12, it is locked in this position by the spring clip 1 5 the pawl 1 6 of which catches behind the trailing edge of the barrier and prevents the door 3 from opening, and in this fashion the "catch" is retained within the trap and is protected from outside predators.The spring clip 1 5 is also used to lock the door 3 in the open position, e.g. for pre-baiting of the trap, the door mechanism 3 being pivotted against the biassing influence of the spring 1 9 until the pawl 1 6 catches in front of the leading edge of the barrier 26 preventing it from closing across the entry port 12. With reference to Figure 1, when the trap is set for catching, however, the door mechanism 3 is prevented from pivoting into the closed position by interaction with the false floor treadle trigger mechanism 4 and in this "set" position the leading edge of the barrier is slightly beyond the pawl 1 6 in the direction of closure such that the door is not prevented from closing when the trap is triggered.

The false floor trigger mechanism 4 is a sheet of polypropylene plastic which in general overall shape conforms closely to the shape of the enclosure base 5. The sheet 4 is cut with two pivots 30, at the center of each of its straight edges, which flex into the pivot holes 1 7a and 1 7b drilled through the sides 6a and 6b of the enclosure, when the false floor is fitted in the trap.

With reference to Figures 7 and 8, the false floor 4 is bent through an angle of about 1 50 along a line joining the two pivots 30, and is cut-away at the corner 31 which corresponds to the entry port 12 when fitted to the trap. Along the edge of this cutaway 31, adjacent the curved end edge of false floor 4, is a turned down tab 32. This tab 32 provides a latch which catches over the leading edge of the arm 25 of the door mechanism when the trap is set as shown in Figure 1, and prevents the door from closing. In this set position also, the false floor 4 covers the door arm 25 and shields the animal from being harmed by the arm 25 when the trap is sprung.

In use, the traps are taken out into the field and set up in appropriate locations to trap animals as desired. Advantageously the trap enclosures 1, with door 3 and false floor 4 mechanisms fitted and the iids 2 removed, can be easily stacked one within another and, in view of their light plastic construction are relatively easy to transport in quantity. If pre-baiting is desired prior to setting of the traps, the door mechanisms are locked in the open position for a few days by means of the spring clip 1 5. The traps, containing nesting material and food as desired, are then set, the door mechanisms 3 being pivoted against the springs 1 9 and the false floors 4 pivoted to hook tabs 32 over the leading edges of the door radial arms 25. The lids are fitted either before or after setting of the traps.Subsequently if an animal enters the trap through the entry port 12 and places its weight on the rear portion 33 of the false floor, the floor 4 will be caused to pivot raising the tab 32 and releasing the door 3 permitting it to close under the biassing influence of spring 1 9 and lock over the entry port 12 trapping the animal.

The animal is then recovered from the trap. The lid 2 is slid towards the front end 7 of the trap and the fingers of a hand are inserted into the enclosure through the gap between the lid and the back 8 of the trap, and the catch is gathered into the hand. The curved back 8 of the trap assists this mode of catch retrieval. Alternatively the catch may be tipped out of the trap into a suitable bag, the bag being held tightly around the body of the trap as the lid 2 is slid off the trap.

The trap illustrated in the accompanying diagrams has an internal volume of 500cc and a floor area of approximately 56 sq. cms.

Claims (11)

1. An improved trap for catching small animals comprises a door mechanism having a door to close an entry port through which the animal enters the trap, in which the mechanism is arranged to pivot about an axis which is spaced from the door whereby the door closes the entry port by pivotal motion across the entry port.

2. A trap according to Claim 1, in which the trap wall is arcuate with respect to the axis of rotation of the door mechanism adjacent the entry port and the door is similarly profiled, such that as the door closes it slides across the entry port in close proximity with the wall of the trap and the internal volume swept out by the door is substantially minimised.

3. A trap according to Claim 1 or 2, in which the door mechanism comprises a radial arm pivoted towards one end and carrying or encompassing the door towards its other end.

4. A trap according to Claim 1,2 or 3, in which the axis of the door mechanism passes vertically through the floor of the trap spaced towards the end of the trap opposite the entry port.

5. A trap according to any of the preceding claims, comprising a trigger mechanism in the form of a false floor or treadle across the bottom of the inside of the trap which maintains the door in the open position and is responsive to the weight of the animal to trigger the trap and release the door.

6. A trap according to any of the preceding claims comprising a locking mechanism for locking the door in the closed position.

7. A trap according to any of the preceding claims comprising a pre-baiting mechanism for locking the door in the open position.

8. A trap according to Claim 7, comprising a latch mechanism which is adapted to either latch in front of the leading edge of the door in the prebaiting mode or latch behind the trailing edge of the door in the locking mode.

9. A trap according to any of the preceding claims, comprising a means of access which is separate from the door entry port.

10. A trap according to any of the preceding claims constructed of a plastics material.

11. A trap according to Claim 1, substantially as hereinbefore described and illustrated, with particular reference to the accompanying diagrams, Figures 1-8.