fig1 schematically shows a bayonet dripper 20 comprising a housing 21 having a bayonet coupling nipple 30 comprising a stem 31 and a bayonet 32 , in accordance with an embodiment of the invention . water enters dripper 20 from a pipe to which the dripper is connected through coupling nipple 30 . water exits the dripper to irrigate a plant or plants , optionally via an outlet tube 40 . optionally , bayonet dripper 20 is a regulated dripper that provides a same regulated output flow of water substantially independent of inlet water pressure for a range of water pressures . only features of bayonet dripper 20 germane to the discussion are shown in fig1 . housing 21 is optionally formed from male and female snap - fit components 23 and 24 respectively that are formed by injection molding as separate pieces and are snapped together to form the housing . male component 23 is optionally formed with bayonet coupling nipple 30 and female component 24 is optionally formed with water outlet tube 40 . bayonet 32 is formed with a sharp tip 33 and a water inlet orifice 34 that communicates with an inlet channel ( not shown ) formed in stem 31 . water enters dripper 20 through the inlet orifice 34 and flows into the dripper housing through the inlet channel in the stem . in an embodiment of the invention , stem 31 of coupling nipple 30 is formed as an integral part of male component 23 , optionally from a relatively soft inexpensive plastic , such as polypropylene and / or soft polyethylene , that is relatively resistant to damage by nutrients and chemicals typically carried by water used to irrigate and cultivate plants . bayonet 32 is formed from an appropriately hard material so that the bayonet can be efficiently used to puncture the wall of an irrigation pipe . optionally , coupling nipple 30 is formed by injection over - molding in which bayonet 32 is formed over the end of stem 31 or stem 31 is formed “ into ” bayonet 32 . optionally , bayonet 32 is formed from a material comprising a relatively hard , wear resistant plastic , such as polyacetal ( pom ) polycarbonate ( pc ), polyamide ( pa ), polybutylene terephthalate ( pbt ), polyphenylene oxide ( ppo ) and / or a composite material optionally comprising a plastic reinforced with fibers , such as glass or carbon fibers . the end of stem 31 on which bayonet 32 is over - molded is optionally formed with at least one locking feature so that after over - molding the bayonet is mechanically locked to the stem . in some embodiments of the invention , the relatively soft plastic used for dripper housing 21 and the relatively hard plastic used for bayonet 32 bond “ naturally ” as a result of the over - molding process and / or contact thereafter . for example , the plastics might bond chemically and / or mechanically as a result of intermixing of the two plastics at their interface . materials suitable for such bonding are , optionally , polypropylene for the relatively soft plastic and a composite material , such as polypropylene reinforced with fibers , for the relatively hard plastic . fig2 a and 2b schematically show male snap - fit component 23 before and after over - molding bayonet 32 on stem 31 and illustrate locking features in accordance with an embodiment of the invention that lock bayonet 32 to the stem after over - molding . features of stem 31 in fig2 b that are covered by bayonet 32 after over - molding are shown in ghost lines . referring to fig2 a , stem 31 has an end 36 optionally formed with at least one protruding rim 37 and a groove 38 . during over - molding , the plastic from which bayonet 32 ( fig2 b ) is formed flows over and encompasses rim 37 , and fills groove 38 . when the plastic hardens , bayonet 32 is locked to rim 37 so that the bayonet cannot easily be torn from stem 31 and the bayonet is prevented from rotating relative to the stem by plastic that fills groove 38 . stem 31 may be formed with locking features to mechanically lock a bayonet in accordance with an embodiment of the invention to the stem that are different from the locking features , i . e . rim 37 and groove 38 , shown in fig2 a and 2b . for example , end 36 may be formed with an annular recess having at least one tooth that extends from the bottom of the groove . the plastic used to form the bayonet flows into the recess during over - molding and after hardening locks the bayonet to the stem . the at least one tooth prevents the bayonet from rotating relative to the stem . in some embodiments of the invention , locking features are additionally or alternatively provided by the bayonet and stem plastics , which bond together because of the over - molding process and / or a natural affinity for each other . bayonet dripper 20 is coupled to an irrigation pipe by pressing bayonet 32 to the wall of the pipe with sufficient force so that tip 33 of the bayonet punctures and forms a hole in the wall and bayonet nipple 30 penetrates into the pipe so that its stem 31 seats in the hole . fig3 schematically shows an irrigation pipe 50 and two bayonet drippers 20 . one of bayonet drippers 20 is schematically shown puncturing the wall of pipe 50 so that it may be coupled to the pipe and the other bayonet dripper 20 is shown seated in the pipe after it has punctured the wall of the pipe . fig4 a schematically shows a press - fit pipe coupler 60 for connecting two irrigation pipes , in accordance with an embodiment of the invention . pipe coupler 60 comprises a tube 61 formed from a relatively soft chemically resistant plastic and optionally two gripping ribs 70 having gripping edges 71 formed from a relatively hard , wear resistant plastic . optionally , as shown in fig4 a , gripping ribs 70 are connected by at least one strut 72 . strut 72 , as explained below , is an artifact of an injection over - molding process used to produce press - fit coupler 60 . optionally , the soft plastic comprises polypropylene and / or polyethylene . optionally , the material from which the gripping ribs are formed comprises at least one of polyacetal ( pom ), polycarbonate ( pc ), polyamide ( pa ), polybutylene terephthalate ( pbt ) and / or polyphenylene oxide ( ppo ). additionally or alternatively , the material from which ribs 70 is formed comprises a composite material . optionally , the composite material comprises a plastic reinforced with fibers , such as glass or carbon fibers . in an embodiment of the invention , gripping ribs 70 are over - molded onto tube 61 , which is formed with at least one locking feature that functions to mechanically lock the ribs in place . optionally , the locking features comprise a pattern of recesses into which the plastic from which the ribs are formed flow during over - molding . fig4 b schematically shows tube 61 formed with a pattern of recesses that function to lock gripping ribs 70 in place . optionally , the pattern of recesses comprises an annular recess 80 for each gripping rib and a linear recess 82 that connects the annular recesses . linear recess 82 functions as a flow channel along which liquid plastic flows during injection molding to fill cavities in a die used to form ribs 70 . the channel allows liquid plastic for both ribs 70 to be fed from an optionally single injection orifice in the die located along the channel . the liquid plastic flows from the injection point in both directions along channel 82 to fill annular recesses 80 and the cavities . annular recesses 80 prevent gripping ribs 70 from moving along the length of tube 61 after they are over - molded onto the tube and recess 82 prevents the ribs from rotating relative to the tube axis . in some embodiments of the invention , as with the dripper , locking features are , additionally or alternatively , provided by the rib and tube plastics , which bond together because of the over - molding process and / or a natural affinity for each other . fig5 schematically shows a cross - section of press - fit coupler 60 connecting two irrigation pipes 85 . it is noted , that whereas press - fit pipe coupler 60 is configured to connect only two pipes and comprises a straight tube on which hard gripping ribs are formed , a press - fit pipe coupler , in accordance with an embodiment of the invention , can be configured to connect more than two pipes . for example , a press - fit coupler in accordance with an embodiment of the invention , can comprise a configuration of a plurality tubes , such as a “ t ” or a “ star ” configuration of tubes , formed from a soft plastic with each pipe having formed thereon a gripping rib formed from a hard plastic . a press - fit coupler in accordance with an embodiment of the invention may also be used to connect an irrigation pipe to an irrigation apparatus , such as a sprinkler , rather than another irrigation pipe . the sprinkler , which may advantageously be formed from a soft plastic , may comprise a tube formed from the same plastic having over - molded thereon a gripping rib from a hard plastic for connecting the tube , and thereby the sprinkler , to an irrigation pipe . in the description and claims of the present application , each of the verbs , “ comprise ” “ include ” and “ have ”, and conjugates thereof , are used to indicate that the object or objects of the verb are not necessarily a complete listing of members , components , elements or parts of the subject or subjects of the verb . the invention has been described with reference to embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention . the described embodiments comprise different features , not all of which are required in all embodiments of the invention . some embodiments of the invention utilize only some of the features or possible combinations of the features . variations of embodiments of the described invention and embodiments of the invention comprising different combinations of features than those noted in the described embodiments will occur to persons of the art . the scope of the invention is limited only by the following claims .
a drip irrigation device for distributing a portion of the water flowing in an irrigation pipe to a plant , the device comprising : a housing formed from a relatively soft plastic ; and a connector for coupling the housing to the irrigation pipe comprising a bayonet for puncturing the irrigation pipe formed from a relatively hard material over - molded onto a feature of the housing made from the soft plastic .