In an apparatus for successively making plastic bags, a laser beam irradiator irradiates laser beam onto webs of panel material and a body of zipper material to heat and melt the webs of panel material and the body of zipper material with the laser beam. The webs of panel material and the body of zipper material are fed intermittently at a speed predetermined to be changed by time. The irradiator is controlled on a feedforward control basis for the laser beam to be regulated in amount, the amount being calculated from the speed predetermined, to obtain a calculated value of amount. The laser beam is regulated in accordance with the calculated value to heat and melt the webs of panel material and the body of zipper material uniformly irrespective of the speed being changed.

The present invention relates to a method for welding two polyamide plastics using a primer, the primer containing at least one polymer synthesized from at least one maleic anhydride or maleic anhydride derivative. The invention also relates to correspondingly welded products.

The invention relates to a method for welding two different polyolefin plastics using a primer, said primer containing at least one maleic anhydride graft polyolefin polymer. The invention also relates to correspondingly welded products.

The invention relates to a method for welding a polyolefin plastic and a plastic consisting of a polymer with at least one aromatic unit in the polymer main chain, using a primer which contains at least one polymer built from at least one monomer with at least one double bond. The invention also relates to correspondingly welded products.

The invention relates to a method for bonding two different plastics using a primer. The two plastics which are to be joined to each other have a weighted quadratic distance between the Hansen parameter (R.sub.a).sup.2 of more 22 MPa and the primer contains a polymer which has a weighted quadratic distance between the Hansen parameter (R.sub.a).sup.2 of less than 22 MPa to both of the plastics which are to be joined. The invention also relates to correspondingly bonded products.

The invention relates to a method for welding a polyamide plastic and a poly(meth)acrylateparticularly a polymethyl methacrylateplastic using a primer, said primer containing at least one copolymer synthesised from at least one styrene or styrene derivative and at least one maleic anhydride or maleic anhydride derivative. The invention also relates to correspondingly welded products.

The invention relates to a method for welding a polyolefin plastic and a plastic based on at least one polymer containing carbonyl groups, using a primer which contains, in relation to the proportion of polymer in said primer, at least 20 wt. % of a polymer that comprises maleic anhydride or maleic anhydride derivative units. The invention also relates to correspondingly welded products.

The purpose of the present invention is to provide a flow sensor that makes it possible to detect temperature abnormalities that the flow sensor has been exposed to and the time history of the flow sensor in a high-temperature environment from an externally visible cover material and that uses a cover material for which the laser welding quality can be guaranteed through visual inspection when the sensor is delivered as a product and even if the sensor is used in an abnormal state. A flow sensor provided with a housing, a cover, a circuit chamber that houses a wiring portion sealed between the housing and the cover, and an auxiliary passage through which the liquid to be sensed flows, wherein: a joint portion formed on the housing and a joint portion formed on the inner surface of the cover are joined together through the laser welding; the main material of the cover is a crystalline resin; the cover includes an amorphous alloy; and the cover is made to have a natural color.

The present invention relates to a process for laminating a first substrate, which comprises a thermoplastic polymer material surface, and wherein the first substrate preferably is a thermoplastic polymer film, to a second substrate, wherein the second substrate preferably is a non-woven or woven fabric, wherein the thermoplastic polymer material surface is activated by irradiation with a laser beam prior to laminating the two substrates to each other as well as a device for carrying out such a process.

Provided is a low-cost flow sensor which improves productivity while maintaining high quality and high reliability. This flow sensor is provided with a housing, a cover, a circuit chamber sealed between these and housing electronic components or wiring, and a subpassage through which the fluid flows that is to be detected, and is characterized in that the welding width of a first welded portion forming the circuit chamber is greater than the welding width of a part of the second welded portion forming the subpassage unit.