Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Greig, J: AUTHOR [+1]
This article describes a bracket assembly on the pick-up head of a surface placement machine which allows complete freedom of adjustment as well as eliminating close tolerances required by the design of the head. (Image Omitted)
This article describes a bracket assembly on the pick-up head of a surface placement machine which allows complete freedom of adjustment as well as eliminating close tolerances required by the design of the head.
The head consists of four carriages which are connected in pairs by a tie bracket. Wheels fitted to the carriages are a further feature and when assembled to the main body of the placement head, friction is reduced significantly, giving improved motion control during the tweezering cycle. The head is driven by special inbuilt cylinders located on each of two carriages (called active cars). The two idle carriages (called passive cars) are connected to the active cars by means of tie brackets, creating the two assemblies as described above.
Tweezering, shown in Fig. 1, is a stage of the pick-and-place cycle which centers the component on the pick-up tool by the action of one or both pairs of tweezers, normally taking place while the pick-up head carriage is moving the head over to the placement position. The sequence is as follows. 1. Compressed air is applied to one or both tweezer-actuating pistons. 2. Pistons raise actuating levers and depress tweezer sleeve flanges. 3. One or both pairs of tweezers (or both pairs alternately) close on the component to center it on the pick-up tool tip.
Unless the timing of the tweezer leg movement between active and passive cars or the tweezer leg assemblies is correctly set, placement becomes a problem creating excessive machine downtime.
Referring to Fig. 2, the design of the tie bracket assembly gives complete freedom of adjustment between active cars 11 and passive cars 10. It also eliminates the close tolerances required to manufacture an existing placement head to ensure active and passive car alignment. The construction of this assembly is described with reference to Figs. 2A, 2B and 2C.
The existing passive car body 1 is modified by adding clamp 3 and threade...