The Swiss have been producing regular-production automatic movements for about half a century. If there is a single automatic movement that stands out as the reigning queen of that half century, it is the Patek Philippe caliber 27-460 and (with simple calendar) 27-460 M. In concept, in construction, and in finish, this is perhaps the most elaborate and costly simple automatic watch movement ever produced.Patek began production of automatic movements somewhat later than most other manufacturers. It was 1953, and Patek released the 12-600 AT, a lavishly conceived, if not quite perfected, attempt at the highest possible quality in an automatic. A number of problems developed with the complex winding system of this movement, requiring the addition of a ball bearing and two jewels. The movement, finally, also received a Gyromax balance wheel and to keep it (and its massive 18K winding rotor) in place, an additional attachment to the case (for a total of three). Seven years later and most problems solved, Patek re-released the movement as the caliber 27-460 and, a year later, the 27-460 M. This iteration of the movement replaced the jeweled winding rotor bearing with a slightly flatter ball bearing and a unique adjustable balance spring stud carrier. The 27-460 was otherwise unchanged from the later versions of the 12-600.
Patek began production of automatic movements somewhat later than most other manufacturers. It was 1953, and Patek released the 12-600 AT, a lavishly conceived, if not quite perfected, attempt at the highest possible quality in an automatic. A number of problems developed with the complex winding system of this movement, requiring the addition of a ball bearing and two jewels. The movement, finally, also received a Gyromax balance wheel and to keep it (and its massive 18K winding rotor) in place, an additional attachment to the case (for a total of three).
Seven years later and most problems solved, Patek re-released the movement as the caliber 27-460 and, a year later, the 27-460 M. This iteration of the movement replaced the jeweled winding rotor bearing with a slightly flatter ball bearing and a unique adjustable balance spring stud carrier. The 27-460 was otherwise unchanged from the later versions of the 12-600.
By today's standards for high-grade calibers, the 27-460 is massively overbuilt: 12 lignes (27mm) and 4.6 millimeters thick without calendar, an even heftier 5.35 with. The 27-460 was to remain in production as the base movement for the perpetual calendars for 25 years until finally replaced in 1985 by the much flatter caliber 240.
A single, large bridge (4) carries the upper pivots of the third and center wheels, the central winding rotor ball- bearing mount (5 ), and two super-bridges (6 and 7) for the extremely sophisticated automatic winding mechanism. The entire construction is, of course, rhodium plated, and finished to the standards of the Geneva Seal. The Geneva seal appears both on the mainplate (8) and the winding super bridge (7). It is customary to place the seal on both the mainplate and one bridge, usually the crown wheel or barrel bridge.
The 27-460 (unlike the earliest versions of the 12-600) uses Patek's Gyromax, adjustable-mass balance with a Breguet over coil spring (right). The overcoil itself is indicated at the arrow. The rotatable Gyromax rim weights permit poising of the balance, as well as adjustment of daily rate. This arrangement eliminates the conventional regulator index, with all the positional adjustment problems it poses.
On the caliber 27-460, Patek introduced another extremely useful innovation, the "self-adjusting" balance spring stud carrier (above and below right). A lock screw on the top of the balance cock may be loosened once the cock, balance, and spring are in place on the top plate. The stud then moves into any position necessary to allow the spring to perfectly center itself. Centering is the key to good positional performance, and no other stud design assures such perfect centering. Beat error, unfortunately, must be corrected by the traditional, tedious method of rotating the inner spring attachment (collet) at the balance staff.
While most calendar mechanisms use a simple bent steel spring to detent the calendar disc, the 27-460-M uses a beautifully machined detent and cut, finished spring. This mechanism is comparable in quality to Patek's more complex perpetual plates and is surely the most elegant simple calendar ever constructed.
The entire automatic winding system is contained on the "main bridge" of the movement, which also supports the upper pivots of center and third wheels. The bridge is shown right, stripped of all mechanism. The arrow indicates the lower pivot of a ball bearing supported eccentric wheel that is driven by the winding rotor and rides inside the arms of a rocker. The rocker (right, 1) is driven by the eccentric wheel between its arms (2). Rocking on a jeweled pivot (3 ) the rocker carries a click-pawl. By means of a lobe (5), the rocker also drives a second rocker with its own click-pawl (6).
The rocker (right, 1) is driven by the eccentric wheel between its arms (2). Rocking on a jeweled pivot (3 ) the rocker carries a click-pawl. By means of a lobe (5), the rocker also drives a second rocker with its own click-pawl (6).
As seen mounted under their bridge (left), the function of the rockers and click- pawls may be understood more clearly.The first rocker ( 1) carries its own click-pawl (5). By means of its lobe (1A), the rocker drives the second rocker (2) with its click-pawl (3) through a jeweled interface (4 ). Each of the two click-pawls alternately winds and holds the first drive wheel (6, moving counterclockwise). A single bridge (7) holds all components in jeweled bearings. In operation, the rockers and click-pawls play an uncanny, rapid-fire, syncopated choreography.
The first rocker ( 1) carries its own click-pawl (5). By means of its lobe (1A), the rocker drives the second rocker (2) with its click-pawl (3) through a jeweled interface (4 ). Each of the two click-pawls alternately winds and holds the first drive wheel (6, moving counterclockwise). A single bridge (7) holds all components in jeweled bearings. In operation, the rockers and click-pawls play an uncanny, rapid-fire, syncopated choreography.
The pair of square jewels on the second rocker (to interface with the lobe of the first rocker) are typical of the wonderful construction seen throughout the caliber 27-460. In this 40 year old example of the caliber, the original automatic winding parts showed virtually no wear.
