There are many different types of devices and apparatus systems presently available on the market for collecting single and multiple samples of blood in one or more different containers with only a single entry into the tissues of the patient. The many different types of structures are designed to operate in a variety of different ways and to achieve a variety of different effects. Valve structures are employed to shut off blood flow automatically as the evacuated containers are interchanged for successive samples. Furthermore, various types of check valve devices are also employed to permit flow of blood from the patient to a container and to automatically close and prevent back flow of blood or other fluids such as medicaments in the evacuated containers to the patient. Additionally with the many different types of valve structures, there are also many different types of indicators employed to indicate when a veni-puncture has been achieved and blood has entered the device so that the device can be coupled to an evacuated container to draw blood therethrough from the patient. The various types of indicators are designed to provide a showing of blood to the operator so that he is assured that veni-puncture has been achieved and it is the proper time to interconnect the evacuated container tube with the system and draw blood into the tube. Actually the indicator which shows blood to the operator indicating veni-puncture should not be leaked from the device so that contamination of the operator or the surrounding area occurs. An example of a patented system which employs the above features is present in U.S. Pat. No. 3,817,240.
Naturally it is always advantageous to provide additional improvements to the overall blood collecting system particularly in the use of valving mechanism for collection and anti-back flow consideration as well as providing an indicator which is positive acting and dependable and which detracts as little as possible from the actual operation of the collecting system while giving effective and positive indication of veni-puncture without the danger of contamination.