A variety of machines are known for loading magnetic tape onto hubs or into cassettes.  Such machines are commonly called "tape loaders" or "cassette loaders".  U.S. Pat.  Nos.  3,637,153, 3,737,358, 3,997,123, 4,06,1286 and 4,062,719 illustrate machines for loading magnetic tape into various types of cassettes, including the Phillips-type cassettes used for audio recordings.  U.S. Pat.  Nos.  4,512,904 and 4,486,262 illustrate machines for loading magnetic tape into conventional video-type cassettes, e.g., VHS or Beta type cassettes.  The audio cassettes and the video tape cassettes are similar in that the loaded cassettes consist of a cassette case containing two rotatable spools or hubs, a leader attached to each spool or hub, and a predetermined length of magnetic tape having its ends spliced to the two leaders.  However, VHS and Beta type video cassettes are substantially larger than Phillips-type cassettes and differ therefrom in that they have (1) a pivoted door which conceals the tape when the cassette is not in use, (2) means for releasably locking the door, and (3) means for releasably locking the hubs against rotation. 
The manufacture of loaded audio and video cassettes is similar in that the common practice is to start with a C-Zero ("C-0") cassette, i.e., a cassette that consists of the cassette case with the two hubs and a length of leader tape having one end connected to one hub and the other end connected to the second hub.  These C-Zero cassettes are then filled with blank or prerecorded tape by means of automatic loading machines of the type known as in-cassette loaders.  In some quarters the term "C-Zero" is reserved for audio cassettes and the corresponding empty video cassettes are called "V-Zero" ("V-0") cassettes.  However, as used herein, the term "C-0" applies to both audio and video cassettes. 
The loading procedure typically comprises the following steps: (1) withdrawing a selected length of leader tape from the C-0 cassette; (2) cutting the leader tape so as to form two first and second discrete leaders; (3) splicing the leading end of the magnetic tape to be wound into the cassette to said first leader, (4) rotating the hub to which said first leader is connected so as to wind a given length of magnetic tape onto that hub; (5) terminating winding of magnetic tape onto said first hub; (6) cutting the magnetic tape at a selected point outside of the cassette; (7) splicing the trailing end of the given length of magnetic tape to the second leader attached to the other hub; (8) winding the trailing end of the given length of magnetic tape and the second leader into the cassette; and (9) ejecting the loaded cassette and replacing it with a new C-Zero cassette.  The procedure for loading magnetic tape into C-Zero video cassettes is the same as for audio tape, except that the loading machine must be capable of opening the door to the video cassette in order to permit extraction of the leader tape from the cassette, unlocking the hubs, and holding the door open during the time that the loading operation is being conducted. 
Because the leader tape in a C-Zero video cassette is relatively short in comparison to the leader tape customarily provided in audio cassettes, the machines for loading video cassettes are more complicated by virtue of the necessity of working with a shorter leader. 
Recently a new form of video cassette called the 8 millimeter ("8 mm.")  video cassette has been developed.  The 8 mm.  cassette case is much smaller than the VHS or Beta-type video cassettes, and in fact its length and breadth are closer to the corresponding dimensions of a Phillips-type audio cassette case.  However, the thickness of an 8 mm.  video cassette is substantially greater than that of a Phillips-type cassette because of the fact that its video tape is substantially wider than conventional audio tape.  A further significant difference is that the leader in a C-Zero 8 mm.  video cassette is much shorter than the leader in the larger size VHS or Beta video cassettes.  The leader of an 8 mm.  cassette is only about 140 mm.  long from hub to hub.  Therefore when the leader is paid off from one or both of the two hubs (according to whether or not the leader was partially wound on one or both hubs), only a short portion of its length is available outside the cassette case for cutting, splicing and winding.  This short length of available leader tape makes it impossible or unsatisfactory to load magnetic tape into 8 mm.  cassettes using a tape loader patterned after those heretofore used to load audio cassettes or VHS or BETA format video cassettes, without violating the requirements of video cassette manufacturers regarding the quality, reliability and speed of loading 8 mm.  cassettes. 
More recently an 8 mm.  video tape in-cassette loader featuring an improved splicing block assembly (also sometimes called a "shift block assembly") was developed.  That improvement is disclosed in U.S. Pat.  No.  4,682,742, issued July 28,1987, to George M. Woodley and William S. Bakes for "Apparatus and Method For Loading Tape Into a Cassette".  The machine disclosed in that patent is capable of loading tape into a C-Zero 8 mm.  cassette having standard length leaders, i.e., about 140 mm.  long, in a manner that meets industry standards as to quality and speed.  However, the novel shift block assembly disclosed in that patent occupies a relatively large space and hence limits the location and/or size of other machine components.  More importantly, the shift block assembly requires a significant number of operating mechanisms, each of which (a) may be subject to breakdown with a consequent loss of productivity unless the machine is properly maintained and/or (b) tends to limit the speed at which the components of the shift block assembly can be moved as required by the desired operating cycle of the in-cassette loader.