GB2230466A - Catapult - Google Patents

Abstract

A catapult has each length of elastic material passing over rollers R3 and R4 to a fixing point B2. Compared with a conventional layout, this gives longer lengths of the elastic material which can be elongated smoothly over the rollers to impart greater energy to a projectile. <IMAGE>

Description

CATAPULT This invention relates to a catapult.

Catapults are well known devices some of which comprise a framework from which elastic or rubber strips are attached. A pouch is attached to the other end of the elastic in which is placed a projectile.

By means of pulling the pouch and hence projectile away from the framework which in turn is held at a fixed position, the elastic is stretched. When the pouch is released, the elastic contracts and the projectile is propelled through and then away from the framework.

The most important factors which govern the distance a projectile can be propelled is the weight and dimension of the projectile, the amount of energy which can be imparted to it from the stretched elastic, and the trajectory of the projectile.

If we consider a projectile of unit weight and dimension propelled at a fixed trajectory, then the distance it will travel is directly proportional to the amount of energy imparted to it by the elastic.

If a piece of elastic is stretched along its entire length by an amount which takes the elastic to it's elastic limit. ie.it will stretch no further before breaking, then the amount of energy stored in the elastic is a function of it's original unstretched length and diameter, plus the material properties of the elastic.

If we consider elastic of unit diameter and elasticity, then the greater the original unstretched length of elastic which is taken to it's elastic limit, the greater the amount of energy which can be stored in the elastic.

We can therefore conclude that for the aforementioned unit conditions, the greater the original length of unstretched elastic which is taken to it's elastic limit in order to propel a projectile, the further that projectile will travel.

Essential Technical Information According to the present invention a means is provided in the catapult framework to facilitate the fitment of a greater length of unstretched elastic material which is capable of being stretched to its elastic limit during normal operation, than is possible with conventional frame configurations. For example there may be rollers or other guides for defining a longer elastic path.

Embodiments of the invention will now be described in greater detail by way of example with reference to the accompanying drawings, in which: - Figure 1 illustrates the catapult framework with rollers and elastic in position.

Figure 2 illustrates the same catapult framework viewed from the side.

Figure 3 shows a conventional catapult configuration.

Figure 4 shows the configuration of the present invention.

Figures 1 and 2 show a catapult having an integral handle and guard, on which is mounted two sets of rollers R1 & R2 and R3 & R4.

Two strips of elastic El and E2 are each routed through guides at points G1 and G2 respectively on each leg of the framework, and then around their respective rollers.

Each strip of elastic El and E2 is attached to the framework at points B1 and B2 respectively.

The rollers are enclosed by removeable covers which are attached to each leg of the framework.

The free ends of the elastic are attached to a pouch which is used to hold the projectile.

With conventional designs, as shown in Figure 3: L1 is the original unstretched length of elastic.

S1 is the distance by which the elastic can be stretched before it reaches it's elastic limit.

D1 is the maximum distance the elastic can be pulled away from the framework before breaking.

In practice D1 is limited by the reach of the catapult operator, and L1 is tailored to give optimum Si.

According to the present invention , as shown in figure 4: D1 remains constant as above.

L2 is the original length of unstretched elastic.

S2 is the distance by which the elastic can be stretched before it reaches it's elastic limit.

As can be seen, with D1 remaining constant, L2 > L1 and S2 > S1.

This means that with the present invention, a greater amount of energy can be transmitted to a projectile for any given standard of elastic than is possible with conventional designs, and hence the projectile is capable of travelling a greater distance.

Thus a catapult embodying the invention generally comprises a framework with integral handle with means to facilitate the fitment of a greater length of unstretched elastic material which is capable of being stretched to its elastic limit during normal operation, than is possible with conventional frame configurations.

The means may be rollers to allow the elastic to elongate smoothly when stretched and then return to it's original length and position when released.

Guides may be provided to direct the elastic onto the correct position on the top framework rollers.

Removeable covers may be provided for attachment to each leg of the framework, for the purpose of protecting the rollers and internal elastic.

A framework which houses the elastic and rollers may be positioned forwards of the handle. (This enables dimension D1 to be increased by the amount of the forward offset-and hence both L2 and S2 are increased accordingly).

Desirably a guard is provided which is integral to the framework, to protect the operators hand from pouch/elastic whiplash.

Claims (7)

1. A catapult comprising a frame with integral handle and guard, means of securing elastic strips to the frame, rollers to allow the elastic to move freely when stretched or released, guides to control the movement of the elastic onto or away from the rollers, and a pouch connected to the free ends of the elastic.

2. A catapult as claimed in claim 1. Wherein catchment means are provided on the frame to secure the ends of the elastic strips to the frame.

3. A catapult as claimed in claim 1. Wherein rollers are provided on the frame to allow the elastic to elongate smoothly when stretched and then return to its original length when released.

4. A catapult as claimed in claim 1. Wherein guide means are provided on the frame co-operable with the rollers to control the movement of the elastic onto or away from the rollers.

5. A catapult as claimed in claim 1. Wherein a pouch is provided, connected to the free ends of the elastic.

6. A catapult as claimed in claim 1. Wherein a handle and guard is provided integral to the frame.

7. A catapult substantially as described herein with reference to figures 1 and 2 of the accompanying documents.