This invention relates generally to bayonet joints of the type wherein a male portion is retained within a female portion and in particular, to a rigid axial retainer for use in retaining the male portion within the female portion.
It is well known that most modern handles for brooms, similar cleaning equipment and the like are made of lightweight metallic tubing. Such handles are often covered with plastic and are widely distributed.
These handles commonly include a plurality of sections which can be combined with each other in order to vary the length of the handle and permit the length of the handle to be changed for each specific need or use to which the handle is to be put. The ability to vary the length of the handle also facilitates packing, storing and transportation of both the handle and the equipment with which the handle is to be used.
The system of connecting sections of handles together and of connecting the handles to an attachment such as a broom or other cleaning device is normally based on so-called "bayonet joints". As used herein, the term "bayonet joints" refers to joints which include a "male" length or member with a suitably tapered end which is adapted to be inserted into a "female" length or member. In order to connect a series of male and female lengths, each length has one tapered end which functions as a male end and one untapered end which functions as a female end. The lengths can then be connected one after the other by alternately fitting male ends into female ends to achieve any desired overall length.
There are many systems for securing the male and female lengths so that the bayonet joints do not become undone during use. In general, means are provided for securing the lengths in a longitudinal direction, hereinafter referred to as the "axial" direction.
In one embodiment, the taper of the male length is provided with a thread which can be screwed into a corresponding internal thread in the female length. The threads are produced by rolling the lengths directly on a thread-forming plate. It is necessary for the threads to be tight in order to impart rigidity to the joint. The difficulty with constructions of this embodiment is that the firmness of the thread spiral decreases after repeated threading and unthreading of the male length in and out of the female length. The decreased firmness that develops tends to pull the male length out of the female length and cause the male length to act against the female length with a wedge action. This in turn causes the edges to be deformed to such an extent that it is no longer possible to tighten the threads properly, and the joint loses rigidity.
In another similar embodiment, the threads of the male length and the female length are provided on separate attachments which are then separately secured to each of the male and female lengths. However, this alternative necessarily increases the weight and the cost of the system.
In still another embodiment, the male length is provided with a circumferential hole. A rounded pin slides radially through the hole against the action of an opposing spring provided within the male length. During engagement of the male length with the female length, the pin retracts within the taper of the male part. Following engagement, the pin is pushed by the spring and extends through the circumferential hole in the male part and a corresponding hole arranged radially on the female part, thereby axially locking the joint. This system does not, however, avoid the drawbacks associated with radial or transverse play of the joint.
In order to eliminate the widespread drawbacks associated with lack of rigidity in units connected by the devices provided in accordance with the known art summarized above, the device disclosed and claimed in European patent application No. 84 83 0295.6, was created. This device has a cylindrical expansion ring on the male part. The ring expands when introduced into the female part by axially striking against a stop provided in front of the male piece under the action of a threaded conical frustum, which then penetrates into the ring itself. The expansion ring is further provided with a longitudinal slit in order to favor homogeneous deformation of the ring. This device provides excellent axial holding characteristics to bayonet joints in which it is used and does so without permitting any transverse or radial play. Consequently, optimum rigidity is provided. The corresponding unit using this device in a bayonet joint is, however, generally too expensive to permit use in brooms, cleaning equipment and the like.