Fractional branching reel-type slot machine

• US 5,569,084 A
• Filed: 05/23/1995
• Issued: 10/29/1996
• Est. Priority Date: 06/14/1994
• Status: Expired due to Term

• Current Assignee: Sg Gaming, Inc. (Scientific Games Corporation)
• Original Assignee: WMS Gaming Incorporated (Scientific Games Corporation)
• Inventors: Durham, Timothy J., Nicastro, Neil D.
• Primary Examiner(s): LAYNO, BENJAMIN
• Application Number:
  US08/447,988
• Time in Patent Office: 525 Days
• Field of Search: 273/143 R, 463/20, 463/21
• US Class Current: 463/20
• CPC Class Codes: G07F 17/3244 Payment aspects of a gaming system, e.g. payment schemes, setting payout ratio, bonus or consolation prizes

Abstract

A method of implementing desired odds for a reel-type slot machine is disclosed. All of the possible reel stop combinations are assigned to unique terminal nodes in one or more fractional branching trees stored in a ROM. The tree(s) comprises a main tier, a plurality of lower tiers and a plurality of terminal nodes. Each of the tiers has a number of entries which lead either to a lower tier or to a terminal node. A random number generator is used to select entries on each tier until a terminal node is selected. The reel stop combination or a particular symbol assigned to the terminal node is then displayed on the pay line and an award is paid based on a pay table.

Claims

1. A method of setting the probability of selection of symbols to be displayed on the pay line(s) of a multi-reel slot machine comprising the steps of:

(a) specifying the symbols for each reel;

(b) providing a symbol look-up table in a memory device for each reel, each look-up table being arranged in a tree branch structure containing tiers of descending probability, each tier having terminal nodes at which individual symbols may be stored and descending nodes which lead to lower tiers, each lower tier having a decreasing probability of occurrence; and

(c) storing the symbols for each reel in the corresponding look-up table at terminal node locations within the tree branch structure corresponding to a desired payoff probability.

2. The method of claim 1 further comprising the step of (d) randomly selecting numbers corresponding to the terminal and descending nodes for each tree to randomly select the symbols to be displayed on the pay line(s) of said slot machine.

3. The method of claim 2 wherein step (d) includes the sub-steps of:

(i) randomly selecting a node in the first tier of said tree branch structure;

(ii) determining if the selected node is a terminal node or a descending node;

(iii) in the event a descending node is determined, dropping to the referenced lower tier in said tree and repeating steps (i) and (ii) for such lower tier until a terminal node is determined;

(iv) storing the symbol assigned to said selected terminal node for display; and

(v) repeating steps (i) through (iv) for each of the reels in said slot machine.

4. The method of claim 1 wherein step (a) includes the sub-steps of selecting the symbols and frequency of each symbol for each reel.

5. The method of claim 3 wherein step (i) includes the sub-steps of determining the number of nodes, N, in the tier and randomly selecting a number from 1 to N to select a node.

6. The method of claim 1 wherein each reel contains a different set of symbols and a separate look-up table for each reel is stored in said memory device.

7. A method of selecting a combination of symbols to be displayed on the payline(s) of a reel-type slot machine comprising the steps of:

(a) for each reel, assigning all possible symbols to terminal nodes in a fractional branching tree look-up table contained in a memory device, said table having a main tier and a plurality of lower tiers, each tier having a plurality of terminal nodes and, except for the lowest tiers, a plurality of descending nodes, said terminal nodes containing said symbols and said descending nodes leading to successively lower tiers in said table;

(b) randomly selecting one of the nodes in the main tier and determining if it is a terminal node or a descending node;

(c) if a descending node is determined, repeating step (b), as necessary, for each successively lower tier until a terminal node is selected;

(d) storing the symbol assigned to a selected terminal node for display; and

(e) repeating steps (b) through (d) for each of the reels to randomly select a combination of symbols.

8. The method of claim 7 wherein said step (b) includes the sub-steps of determining the number of nodes, N, in the tier and randomly selecting an integer from one to N to select a node.